claimed as ne-w is: 1. A iiiethod of regulating the combustion 80 of fuel in a ftiriiace, coii-il)rising contliiuousl.)r kvithdrawing a portion of exhaust proclucts of combustiol-i fi-oill said furnace, inixin(Y said poi-tion ivith t quantity ()f a;r, burniiig any combustible gases in said procl-Licts, an 8.5 controlling the supply of coinb-Listion supporting gases to said i'uriiace iii accorcl-,nce ivith the cli ren e n temper-,It-L.Tre of said exhaust products e re aiid after ignition of any combustible content thereof to iiiain- 00 tain a minlinum of coinbustible gases iil said exhatist products. 9@. A method of controlliiig the combustion of gases in a furnace, coiilpr sino, coiatiiiuously withdraivino,- a portion o th'e 95 exhaust products of coiilbustion frol-n said furnace and mixiiig the sanie wi'Lh a qtiantity of air, bur-nin(y coiiibustible ,cyases in saicl proclucts, ilnd contiiiuously coiatrolliiig the gases supplied to said furn,@ice for support- 100 ing combuslion to increase the proportion of air supplied ,ts the tenaperature in s,,tid I)ortioii i-ises after buriiing any combustibles. 3. A iiiethod of, reoulatiiiff the combustion of fuel iii a ftir-n-,tce, (@olllprising continuously 1 ivithdraiiinu a portion of the ex',-iai-ist products of combustion aiid ieixing the same with a quantity of air, bui-iiing anIT combustibles in stid p@rtion with said air,'and graclilaily -varyinu the volume of COMI)Ustlon support- 110 ing7 ases supplied to said furnace to ri'laintaiii the temperatures of said ex]-iaust gases before aiacl after buriiino, substantially eqliil. 4. iiiethod of repulating the combustion of fuel gases in a ftirliace, coii-iprising coi-i- 11-5- LiTlUOUSI)T testing tlle proclucts of combiistioyi from sal d furnace for uncojisliiiied 'Ltiel gases aiid atitoiiiqtically i,arying the proportiol'is of ,),ases stippliecl to said furiiace tost,,pport coii@bustion to liold to a minimtim the qlian- 120 tity of -Linconsumed fuel Yases in saicl producis of comblistion. 5. A comblistion re(yulitor for fur--,i,,tees which comprises ineans for ivithclrawij-ig a sample of prodlicts of combustioii from a 125 furnace, means for mixi-ng air witli saicl sample, means for igiiiting said sample aiid air mixture. n -ieans for co-ntrollinu the supI)ty of combtistion si-ipporting gtses to IL-lie furnace, ,tnd@ meaiis responsive to the differ-

ence iii t6iiij@6i-a@iire'of @@lid s:imple aincl @,-Lir tu e re an a iiaix re b' f o cl fter igiiition f6i- o;ov,6i-ninu tl-ie operation o'L saicl coiitrolling means. "IV 'c6iiibiis,tioii r6(yul@.tor for f-tiriiaces, whichcomi@rises tl-ie 'c'oiiibiiiatioii of! for withdi-awino- ,t 1)ortioii of t'Lie flue ga,ses, me,,tns @'or mixii-ig saicl po@tion of flue @,Y,,Lses -vvith air or oxygei-i mel,3Lns foli(yiiit!Lio,, sii-d mixtlire a set of resisfaiiee theri@i6ineters 10 positioned to iiieaslii-e the teinl)ei,,itiire differeiice.of saicl portioii ()f (,-a@ aiid aiibefore .and @fter i!zniti6n, a colit,,L(@t pointer a'ctecl 0 in 6pposite directi iis by electric et,,ri-ents throu,o;h sild thermometers,, a @ iii6tor driveii @l,,,iiilper' I)ositior,ed to control the dr@tft to saict furntee, a motlor 7for diiviii(,- said C r, braiieli electric circuits coiiiiected to 1!0" t,Mltl@ees,,tid iiiotoll in oppos'it(, directioi-is, aiict "O cont,,icts Ol'i said eireiiits arranged to bc@ alternately co_niie'ted to a so-Lirce of etiri@Ont by c fhe 'Movement of s@icl contl,ct IDointei! ii-i op site clire6ti6ns. @.O'i-V c6mblistion re(yul@tor 'foi, ftiriia,,@c's whicli c6m@ri es the c6iubination of me,,tDf or withdrii-@ino,, ,t,port.i6,.n of th,-, flue iL)@ases fror.i said T,tirn,,ice, naeaiis f6r iiitroduc,i@@, @ir into saicl ])ortion of flue - 2-ases, ai-i electric for said @tir and - L@or@loi-i 6T fiiie (,,ases, illeans@for IIL'Ilxln(- anci i(;niti.ii,), said flue (Y.1ses and stid air, all el(,ctri.c resistanep, thei-iroiiieter l@ositioned'in said o-ases befoi-e if,:iiition, a second electric re'sisctnce th'ei-inoiiieter in saicl @-,.isos @ftiai- io,-iiitioii incaiis coii,.iectiiig Con4 let C.aid iherilloillet6rs in r 11'el t pa, a p6inter aettilteci in opposit6 clirections by said pai@allel c;r6uits,' aiid a nio'uor for i,@irying the s-d pl of 'combustion siij.)pol-tiii(- p y to said furnacg, controlled by the MOATEn-len@IS'Of saicl c6iitact point'er. 40 8. A com'bustion @egiilator for filii@iiaces r iii coi-iil)rl.slli(, I-iie,,Lns fo ixiiio, a porti6n of tli6 ('asoo-L--s proclucts of colyib-Li@ti6n froin a tu th rnace WI a gas, iiieans fol,'bi-ino-iiio, stiid ,(",Is iiiixtiire to a proxililafely its i6niti.on p 4r) temperature, i-neans for iiisuriiicy the re@,iction Of al'ly coiiib-rtstibl,e Avit'ii ai-ia, fi,ee o:@3,gen ii-i s@id niixt@ire@ n-ieaiis for sti@l)lyinocombtisfion suppidrtino(@as to the' 'furiiace, atad iiieaiis governed by the rise i.ii temperiture 50 of @aid gas mixture due, to said i:,(,actioi-i foicontrolling the supply of Coillbusl@- 'loll stip1,)orl-iiig @-@ases to the furnace. 9. A iiiethocl of regtiltti-n(, the coiiabtistioi-i in a fui,nace coiiip]L,isinc@ testing the ex.55 1 1-iaust c6iaib-Lisfion products to detect Coll'ibi-istible iiiaterif,.l thei@eii-i, ftlil ,tii@t a'r to the Turn ace ai-ict u..tilizin, thc,. test f-or co:ntiiiiio-Lisly contilollintlae,siii),,)Iv of a-i.r to the furnace in@orcler to 'miiiitpiii i, 60 s ubstantially cofnplete con-ibtistioii of stid (Y,t,ses in the' furnace. 1 644 utiliz'ii-lg the test for continuously coiitralliiit),, the suldply of o@,ises foi@ s-L,,pportii-ig bustion to il-itiiitair, a stibst',,Intia'i.lv coiy@p-!ete conibus'U--!oii of ftiel iii the fui,-,iace. ii. A riiethod o'l regt,,iiauin(,, 'u-he -loiiibiis- 70 tion of fuel iii, a ftirn-,tee coriprisl,.ig talz:,,I(l a,,@@aiicij)le of th-- exbtlls,b (@ol-ib,,Istion i), oOL,,ic@('s, ni@-.:iiig tll(' stille witl-i Iir, p"lssi!,i tl-,e m@-x9 tut-e throu(4,-I-i a contact iiiq-tc,,r:!-al to bui,ii @@oiiibustibles Lhei@ein, ,ii-id coiiti-ol'iln(ly t'lie @@3ut.)i)iy of coilI.busti6n sLtl:)poi-tiiip- ('as--s to slid ii,,,,ee iii accordaiicp, in,ith tle, ct'llflei-,-Ilce o@@ I . tempei-ature ir. saiel -_,"4-ep I)a,,,siLD(I tlll'Oll@)'IIL said coi-.ttact iiiatei,it-1. 12. A ii-ictlO(@ of re(yi@tlqtirig Co'C"lb--,@s'L!oD @ti a fui@iiace, coliipi.-isiii@,,, le of tile p exlitust coi-fbiistioji sanie )vitl-i iir, tli(, W,: t -Lx 0 sl,-,ailt-ia'lly the io;iii@@ioii te-nip(-,r,,Ltt,,re o-f,@ coitib stible 'n saicl prociticts, u I i-Iii-otiyh :,t coP-'La@t 1,C) the colfib-Listible there'ii, aii,,l the iciiperatu,.@e di.fference o.L saic@ b.,-7- foi.@,-, @t-iicl tf@ter passii-i@), it tliroii(-I-i tlio colitact riatei,ial A'or conti-olli-iiclr Lli.., 01 coi a@ib-psi-.1'.On siil)p6l,tiii(-r g,-ts,3s to saici 13. Tlaat stel) in the iiietli6c', of coii:ibtistioii which coii-lprisee, I-,nixili- Avi'Lli, (yas contiiiiiiig a loav concei:@,"uia-luioii of cor@-ibusti.bles, b,,ii.-iiin,(,y the riixtiii,-- @iiid the teii-il)ert f (Yas @' t t,, be.- ti,@i-es o t n,i.,@ illr fore ai-id afte,- b@irnino- the 14. rii,,Lt st6p ill tllo lll(,'tllo(l (-"f coi-li u-i@o',,Iiil( Col@ (Y LIbilsti(il@, ColliprisiTi- liiiriill( (oiitaiiiii(', a loai, concenti@@ition of- coiiibli-,tibles Avill.h t colnbustion catalyst, and iiieasiiriii,i@ '@iitemperattii-es of s i.d gas before an@L @after btii@nii-io, the saiiie. 15. 11, a Tleti-lod of coliti@olliilo-, coliibi.i,,@iop., the an,,tlvsis of (Y,,,s contii-Iii low coiicc@ii-n(, ti-,,ttion 'o' f coiiibtisti-blbs coml)i,isin@), ail- ii,ith said o,as liet, till(, s@ii(I c,.:as to 11)Pl@oxtl-ie iii col-flbtistibles bi,@rniiig the i-ii-ixtlll.e ancl in-o- the '("LIS teii:ipei@atLii,,-s be@16i-e ,,tiid ai'@ ciI)ul.niii@-)- the same. 16. That step in ,t iiiethod ol@, combti,-,@t'loii coi-tpi,isil)(-, I)Llssillg V., coiltaitii.iio- a loiy, of cll)rii'bul@- 4-1 tibles in colitact ,@IL.1 coil@ tliei.i biii-ning the a (@oii:,- 1)1.lst@on (,,atItlyst, passing tli,@ @!as ',.-,-,to cc),-itliet AAitli a gecoiid resi ' ai cc stib L @l Oi@ s tially siiiiilar to s id fii,st coil, dr,,d , the teii-il)eratiii-es of the )-as boT-. ore COII'11)iist,ioii by the resi. t'aiiees 6f S"LI(IL Coils. li. The c6iiibliipt',)n a f,)-,Iis - saiiiple t@,,inei-, two resistaiiec Ay,-res iTi si,"@'t @conttiner,'@in electric'ei.i,eiiit Toi@- c-,ch coi-itact 'n-ieinber ii-iolli@tecl in'said coilt@tilioi@ betn@,een said ivires ari-aiige,,l fo 'btii-.ii io.@A m.ethod 6f reglilating the'coffibus- passilio, fr irf@, to tl, I Om one w le o I.el-., tion in a ftirnace, comp,@isin(y c6ntinu6- Lisly iII6,ITIS foi' indi6titing the differ--nee in curtestino- the exh ust com'bustion roducts to reiit, flow throu@,yli s@tid ivii,es. .5 a p 6 detect a;n-v combustible materiil tlierein tnd 18. The- c6nitination of a (yas sarnpl6 coil:-

1,644,123 tainer, tavo resistalic,, wires riiounted in s-qicl container, Pn electric eiretiit l'or each -wire, ineaiis to introcl-Lice air itito gas passiiig through saicl container before the gas reache,@, the first of saicl -1@Nlires, a cont,,te@ meiiiber iaio nte iii saicl containei,s betiveen said vvires arraiaged to burii gqs ppss'lii(,- -,@'roLi oii(,@ -wire to the other, and i-iiea,.is 'Lo@- iiiclicating the diff ei,eiice in curreiit flow thru said ivii-es. io 19. The combinati6ii of a (yas stiiiple container, a con-ibustion catalyst iratin't-ecl i,-i s,,ticl contai-iier in position to force gas passiiig throti(,,h said container to floN-, throucli said catalyst, and separate inepns mountec iii said 15 coiit,,tiner it opposite sides of said catiliTs,@, arrangoi to me,@,sLire respectii7elv 'uhe teiiil. i)erature of tl-ie gts before aiid aftei- passlii,throtigh said cttalyst. 20. The coi-iibinatioii of a o-as saiiiple conO@Q taiiier naeans for causilncr flo w of gas 'ilirougIL the contain-'r, a combus@,ion catalyst mouinteci in stid cont,,tiner i7-i the patli of flo-vn, of tl-i(,. c,as, iiieans for iiiixing air Nvith the gas floiv&, ing throuo;h said coiitainer, @iiid separate iiaeans inounted in sqicl contaiiier at opposit(,@ sides of said cat,.tlyst arrlnged to iiaeastire respectively the tei-iiperature of- the gas before and af 1'er pltssing throtioh s,,tid catalyst. 21. The conabination witli a ftirnace ol,: @O naeans responsive to tlie pres@,iiee of coii-ibi-istible constituents in the gaseotis products of combustioii leaviiic, the furiiace for autoiiiciticallyreotilating the ratio betiieen the rate at ivhich T'uel is actually burnect in the 1-uri-i,,tee Lind the rate -,@u A-vhich air is suppl;ecl therelo foi- thecombtistion of the T'uel. 221. The combii'lation -with a furnace of .,@ieaiis i,esponsive 'Lo tlle reseiice of coiiibustible consl,-ituents iii tb@e ga@,eous prod-Licts lea@Tino,@ the furnace --For automatically decreasiiig the ra'tio between the rlte t- -wliieh fuel is ae'Ltially bui-ned in the furnace ancl 'Lhe iate at iviiicii air is stippliecl for its coiiibiistion on an iiierlase in the rel,,ttive aiiioupt I of sa'd coiiibust,'ble constituents in saicl proclucts. 23. Apparat-Lis for regulating coinbustioi-i in a furnace coinpri,,iiig iiieans for oxidiz4ng coiiibustible co--,istituelits of the gaseoug 30 proc'Lticts of coiiibustion Troli.-i the T-Liriiace, i cl iiiealls i-espoiis've to tl-ie ali:iotiiit of o.@l,in 1 clation pi-oduicecl for atito)iiatically decreasi-l,g the ra",io beL'Weeii 'U-he r,-,te at ii,hich ftiel is aettially burnecl ;.n 'LLirnace and th(, -@5 rate at vvl-iieli air is supplied 'lor its coiiibustion, qs the aiiiouiit of saicl oxidation in, el,e,ase,,s. 24. Apparatus for @egulatiiig combustioii in a, furiiace coiiliprisll'lg in coiiibiiiation co mealis tending,to mai,-itain the ratio betweeii t.1-ie rate at vvlaich 1-uel is actually burnecl iiA the furnt,.ce and the i@ate at which eir is sup pliec[ 'Lor its coiaibustioli in excess of 'Uhat a'k, ivhich con-iplete coi-iibustioii occurs, ancl i-,ieaiis autoliaatically i@espoiisii,e to the pres, c5 etice of coiiabutstible coiisti-tuents in the procl ucts ol' combustioil leavino,- the fureace for clecreasii-ig saicl ratio as reqiiirecl to keep th,-aiiiouiit of said constitueiits si-nill. 25. TI-ie coiiibinatioii with a 'Ltirnace hav - 70 ing a combustion chamber, a fuel stipplyina iiieans aiicl an air suppl,ying means, of means for automatically increasing Ind d'i-ninishp - ii-io- the air s-Lip lied as the amoliiit of combtisti'Dle coiistitueii'ts -in the prodilets of t' co-,-.qbtistioii leaving the flirilace increases ,til-d diniinishes. 26. The i-nethod of conti,olliii.o, furnace con-ibus'L-lioii which inclucles the steps of preheating flue gas from said fur@-IIce ancl callsi-,.-io,- tl-ie coinbustion of an uncoilslimed elemei@.t of coiiibl,.stioii reiiiaiiiing thereii-i, aild utiliz,"liothe increased teiiaperature resultilig LI ft,oi-ii the coiiiblistioii of said flue gas to control t]-ie supply of an eleinent of coinbu.-tiod S5 to the furiiace. 27. A metiiod o'L controlling furiiace coiiibusli-oii iviiieli includes tl-ie steps of heating Liue gas froiii saicl furnace to substaiitiall3t -its lgiii-tio--i teli-iperature aiid b-Lirnii-ig an un.@ 90 constiiiied eler-,aerit of collibustioii reiiiaining tlierein, conipari.,ig the heatino- effect of a qliaitity o' fllie (,,as so ti@eated L iaith a staiid, arOL of compariso.-i, and regtilatino., the si-ip. ply of an elei-iient of coii-lbusl@iol-i to tlip@ fur 95 iiace in accordap-ce ivitli slich coiiiparisoia. 28. The iiie'uhocl of controlling furnace combustion w'ilicli ineltides exposing a teiii, pere,,tui-e respoiasive meaiis to flue gas, cau,,- ino, the coiiibustion of an eleiiient o-T coiii, 100 b ustion reiiiainln(,y in said flue gas, exposing t secoiid teiiiperatt,,re i-esponsive iiieaiis to @ulie increased L(,inperatlire cau-@ecl by reason of s-aid comb-Listion, aiid coiiti-olling th6 sup@ d -L iiient of coriabustion to the ftiri)!,T o' ali ele 105 in accordance ivith said teniperatur(, respoi-isiie n-ieaiis, subst-@Liitially as describecl, 20. F-cLrn,,ice control apparatus includini), n iiieans for causill(Y coilli.)ustion of an unconsuiilecl element of coinbustioii i,eiiiaiiin(y ill 110 tlle flti-I gas of the furnace, aiad iiieaiis aettiallecl in accorciance Avitli tlle Coliaparative heating effect of ), qliantity of gas so ti-eated with a staiidarcl of coniparison, s-Lich iiieans beidg effective for controlliiig a supply ofan elon-ient of coi-nbtistioii to the furi'lace, substantially as clescribed. Iii testimoiay iihereof I affix iny signature. JOHN WILLIAI\L GRISWOLD.

.Patented Oct. 4 1927. 1964491 23 U@41TED STATES PATENT OFFICE. jOi-IN WILLIATI Gl',,ISWOLD, OF 1,VA-RR-(,',I@T, 2ENl\T'z@4YLVA1\TIA, ASSIGNOR TO HEITRY L. DOI-IERTY & COXPANY, A CO:PARTNERST-TIP COMPOSED OF IIENRY L. DOHERTY AND FRANK ITT. VRUEA'UFF, Or, INTF,-%g YOII,'i:, iN. Y. METHOD OF AND A:P:PARATTJS r, OF. CONTROLLING THF, C01VIB USTIO N OF FUFL IN FURNA CES. Applica-tion filed Feb@-uary 12,1920. Serial No. 358,017. This iliventioi-i relates to a n-ietl-tod of ,tnd apparattis Tor controlliiig 'uhe combustion of fuel in g furnace and iiio@re particularly 'Llo ,i combust'on coiitroll;ng niethod and ,tpparatus in which the combListion of -IL2uel is contro'lled@ by the compo-itioii o-l-' the flue -9-ases to ob'Lain the mosc effective v(-,iitilation for the con-iplete coiiibustioi-i of tl.le 'Luel. To oblu-,@tin pei-iect coinL-ust@-on of 'luel, it 10 is esse-,il.ial that sufficient air be, supplied to 4- ul li-, furnace to completely burn all of the ftiel Iiid prevenl, any unb-Liriiecl comb-Listible ('as,@s froi-a ptss@,n,)- olit, of the f Lirn-ace @vith the fitie gises. Ho-wever, ii-i order flo obtain 15 the moslu- efrcient utilization of the heat of combiistioii -with the, inost aclvahta,o-cous f-tan-ie I ten-iperatLii-es, a lai,--c excess o4@@ air over that necess,-.ry for coiiiplel ' combiistion must be Pvoided. An excess of air 20 telICIS to JoAyei-- the effici-ep-ey of a stcaiii boiler bee@-,-Lise, it cools tli- flamp-@ t-liereb-N7 intefer'tng @vitii coinbu'sti-on ancl inereqsc@ the vol-iliiiie of the fl-Lie ,,,q,ses, thei-el.)\- iiiere,-sii-i(r the qu,,t--Lir@it@y o@-'F heat absorbed in hea'@-1- 25 iny the excess gases and tlle quan'u-ity of he,,it c@il:rlec,l fr6m the furiiace by the exhalist o- ,@es. The ii(,-,,tt losses calised by incomplete coinbustio-.i of the fuel are, ho-wei,er, o-ro,,iter thiii those due to the use of excesilo since the hea' absorbed in heati.D(y tl-ie excess ,tir from acitiospl-ieric temperature to the teinpolat-Lire of tl-ie 'itue gases is biit a frq-ction of thequ,,tntit), of lieat in)7 olved iii the combustion 0 , an equ,,,l 35 ,imount of fliel gases. It is, therefore, de-.i-rabl.e to so control comb-Listion as t6 avoid the occui@rende of unconsuiiied coiibiistible gases i-,i the combtistion pi@odiiefs evei). thoLig,-h "I sinall amouiit of free ox.NTge,.i miy ,,o ilso be presep-t duo to air leal@:,tge or lack of uniforinity ill the distribtition of air to ,@lie fire box. The preseiiee of- iincoiisumecl combustible fyases iii the I)rodticts of combtistion may, 45 in certain c,,tses, be indirec'ly detected by ,t detei-inin-,Ltioii of the amount of carbon dioxide in I the flu- gases and D. kiiowlecige of the empirical rel-,tt;lon bet-ween the -perc,-jit:i(Ye of carbor, cli-oxi-Oe -@nd the qLiaii@it,-v roo of tln.-,onsunied coi@bustible gases. For ii@gtance, in 'c-he con-ibtistioii of a 'Luel -which @s con@posed cLIp@ost entirely pf boil, iiearl y all of the oxygen of the air comb-'L-Ties ii ith carbon to f-orm carbon dioxide, and the p (-rceiitage of cii-bon di.oxide in the flile 5, -) g 'ases when perfect combustion is obtailled il lill accordingly be approximately the same a s the percenta-e of oxygen in the Lir. If t he compositio@-of the fuel is changed or if f uels h-Lving i,arying),, proportions Of carbon 6 o a nd hydrogen are used, or if there is an air l eak or ai-i Linevenness in the fuel bed or in t he cipai'l the reo--Lilatiop- of the combustion w'll accordiiigly be rendered unreliable,. T.he primai-y object of the present inveii- 65 ti oil is to provide a metliod of regLilit'Ina t he combustion of f uel in a @ftirnade in wl-iiel-i the stippl3, of gases for supporting c onibus'Llioii in the furnace is controlled clir ectly b)@ the quantity of uncoiisumed fuel 7 0 g ases in the products of combust-lon from s aid f tirnace. Another object of the inventioii is to pi@oI Ticl,-- an apparatus for re,(@lulating the comb,,istion of fuel in a furnace by which the 7 @5 supply of gtses for supportiiio- combustioii to said fiirnace is controlled by the quantity of unconslimed fuel gases iii tl-ie products of coiiibustion from said furnace. Another object of the invention is to pro- 8o vicle a method of controlling coml)tistion by which the air foi- burnin- a- liquid ftiel may be clirectly and accuratel3, controlled to o,i.ve a subst,,tittially perfect combustion of the 'uel. 85 A further object of the invention is to provide an apparatus in which the supply of (yases for supporting combustion is coiit-inuously iinder tl-ie, co,,itrol of the - composition of t,he filie gases. 90 , With these ahcl other objects in vie-w., the invention consists in the process and - app,,,Iratus described in the T-ollowili specifica9 tion and defined in the clailUS. The various features of the inveiition are 95 illtist-ratecl in the accompanyino- drawii)o-s in -whiel-i: Fig. 1 is aii elevation, partly iii section, of a, boiler fiirn-@ce hai@in(- -,i combustion regiilator applied thereto, emboclyino, the loo preferrecl form of the invention; I . nd zn Fig, 2 is a detailed sectional view of the comb-Listion controlling mechanism. I the embodiment of the invention n

CIA 1,644,123 sl)6w;i 1-i-i tl)e tlle (,OlnbListion regulitor @is ,ippiiect to Ln oi o gas btir-Liin,(,r steaiii bo;ler of the water tiibe, t3TPe. Ait, for sul)porti.-ic', the combustioii ,5 of the - @1[iol is J'c)i@eecl bIT iiiea,,i,s oT- a fan 10 tl-i@ouo@h aii a,@r siil)pl.y coi:ictitit 12 to the fii@e I)ox 14 6f the boi.lep. ' The tir l@'i-om IL-he (@Oildiiit 12 floivs tliroiih a I)uriier 15 to a fltiid fu,@l (@itlioi- oil 01.@ g,,is) is 10 dol.i-ve,,,ed by ,i vat-,,,ed pipe 16. Fi@om the @ire box 14, t'ile p,.oclticts of combus"-ion pass I)acli ancl fo@,!th a baiik of wa' -er tubes 17 tnd lea-,,-e the boileifui@nace througli a fli'le 18. @ 1.5 Iii lu-he opei,,,i;tioi-i of the l@@ii@iiace 14, a sai@:iple I)oi!tiol'i of thc, fl-cLc,, -,L@ses is to open the daiiiper, Nvhile, wlicii tl-ie contact is iii,,tcle iii the opposite clirection, tl-Le ii-.oilor be ol)ei-dtecl to elose the cliiiiper. To accomplish this, a small portion of the i'iuc (rases passinr,y tliroii(@h lu-Iie flue 18 is i' ivithdi@-,t-",n througb ,t g.).s stjiiple cont,,iiner iii the foi@ii-n of a sliuiit I)ipe 20 connee'Led to the flue l@8 qtf eitlier end bi, bi-anch pil)es 22 and 24. Air foi- supportin(y tlie coinbustioii of any combtistible n-iaterial pass-,n(r tliro@i(yh '5 the q@liLint pipe 20 is iiit-rodvced -L-hrotigh a pli)e 26 leadir.@). froi,-t the air si,-tpply conduit 12 at-id extenclidg i, clista-,ice iiito the pipe 20 in t dii-ee't-lion pai-allc@'t to LI)e axi@,, of the j:@ipe. TI-ie tempernttire of- tlle (,,ases in tl@,e 80 j@ipes 20 ancl 26 is rais@ecl to ,tp ioximitel3, p m 0 -ipei-tt'Liire by n-ie fi-o tle fille IS "Ijid lyzocl ai-id the ,tiicil th6 i(yniti n teii ans@ of aii 3'sis is lisecl lor iii@"re,,,s,,ng ol@ @tecl,-a,3iii(y tlit@ electrl-c lieatinc., coil 28 @yitliin the piil)e 10 ,i n "I e j@, r s u,@ e -L- i i e o' a s t 6 b e a ii, F@-Lii'i@o-Lindin@,; the I)ipo 26. At the xi@ P, LI' ?O i 'e- o@on i,,i a le coi@,- cii(-l of the p'pe 26 the air supplie-,l fro C@-I x t ivi-th ai@ or oxy 'n - - D m th 85 Lft . ir-er anci ti-ie r,-iix'L-ui:e i@,, 'LIacii he,@ltecl to t pil)e 9.6@ is iiii-xed initli the san-ii)le of fli@,,e t(@l:,il@'el-@ature h@ch is 'h: tlae pipe 20, and the niixtti-re of aase,- 1) II)T is,,@,es throi@igh i pl,,itinLill-@l giilz"@ CIot'ler i itioi te ILI'E, C, co. c i a,)r be coit@,,iiied ii,, tlte flti-, o,,a@.cs. matei-l@,i], @u'O to -instij-,e tiie conipleto, - r o e 2 6 - w " l t l i 1 0 TI, e ur T@ xi liniol@l of the oxygen f ill tl)e PIP is til,'el-l i).,ie:astired I)A, iiieaii@-, of ai-@ any (,oiiibListib](@s cliaivn tlli-otI(Yh ti-ie pipo 1-1110,-Ileter, xtti i-c @@s 20. T'lic oi@ g@ises then pisses fr("Il-l the the ]Ili p',i,-sed ,.i coiil-@let 6r ciiil,,tl@,,-i@(@ Ili,, 20 tliioli h the 1)1]@)e 24 to 9 o Llilete tioii of 18. li t nstire tli@, )@' e teil-il)ei@ature of the -nixtui-e ol! 30 37 I A-NTli'l@cl i i-,i L 1) eTitel.illt4. t't-i-ouo,li the c 95 p i p e s 2 0 2 6 b e f i @ o l , ( , - i ' a c ' u e,ii' iii the 1-@L@ tillil(l, 111,C@ coi-ii b,?,,i(, i(,nited by the co@ I)tls@L'Ible slibstpnces iii tho crp.,Scs, t,i(@ t6iyi ii,,e@isi-tred by mei.,is of ,in cleetric l@esi.stiiiee of the o-l@ l@@;o 32 co--;).ne(!ted: tl)r6Ligli @t bi:,,iiiell in thi,oLi,,-Ii tllo 34 to i bI'L'tc, o,., o4l-ior soii-, 1 - , rial L-Y a-riioi-,,nt 1,.)l-olioi-ti6ii,,,I, to el(,ctric current 36. Tho t@-ii I iperatu@,@,e (1-f ,L-@i,@@y Of, ("oilifter p,,is ql the jil@ll t(Ill,@l@ize 30 is j.)) -ic, 1) @l I I e C) ii @iiis a,:i C'iC-'-' t7 l @6ii ,@ L a c is tli(@i-inoinete,,@ 38 c nO,'-e,,l to th.e electric i.esi24tai),cc,, therlilo-,,iie'ter. '- LI),e 'Llii-ou,)-ii -,i, bi--tneli eircu'Lt 40. The r C il ,I-,:c colill",@l@t@ d .n p,,iz-- flo)vin,@y (,Iit@oi,igii tl@e t 4 0 i e,,'Is,Lance tl,(,i,ii, I all.elx ill I bti-I'Loi,@, cij'cuit i@-hic@'ll i,,icliicl@es Ili 1"lonletei@s '02 @ifid' @'8 j,,, (.,atisecl to each ppila-Ilel br,,Liiel@i a soleiioicl. Po@- ,itioii-@i to posilil@, ,,@ol6no;cls conttiolliii(y ,in clectroiiiagcrea'Le opl)osin Ple(@tioiiia(,,not@c TI@ie iieti(t coiit,,i t 1)oi f i,. 9 n I)III.-Pose, t@lic, -ill et,-Ii bil-I@ll-icli o@i@ '.s o 'I,t '1' tlte to 'IP a eralz,Iii'(@-, oil. tlit@ I)att@ei,y 36 ditisl@ed tit@ I 1etlii@oiigii tli@e ],)"aii(@ii c:,i;- 110 c,,--,d @ii-e t@ie 'L:'Iie ei:,it aiid il@i(@i@-,i@,6--liete,., 32 @s C(li@,U f cillces. Of ti@e t@ o solelloi(@is ti, ]@otl(,"I,l .11 I @l, to @@n"! (p]-)Osll tui,e of ilie t,l-,e secoli(I b@'Lt(-, y t@liroi, li ,i i, e'k-@ U@ i, i i Ay c 4 C). S; c fo '@l, the @U pi,e@;(-,iice o., i.1 t@lic o;' ftlic tli,@-oLiz,,@'l, the bil@,tneli 4-f), 0 ci the i:e,@istan@-e tl-iro-tigl@ tl@e t-lie-,,iiioi@,@ef,er iii'8 @i n I @i wii,e 48 to a secoifd sote oi @'D er,-,ap,es, the curi-,@-nt cleer,_Iase,,-@ 0")r I rc-SI)Olati- create iii e.'.ecti@omagnetic force it-igly, ti-ie tliit of t.',,,e: solenoid 44-. From tl-ie 120 @-,ted bv the solopoicis b,-:,coii-ie Lil.equ@@-. 'rii@@ 50 the -,ui,i@ent 7ettirlis through tli(a ret res iilfrLDt forr-e ol.-,. t,!-,ie so'iC,- iv@lre 4@1,6 'uo tlie@ battei@y 36, T'iie iioiO,c@, tlic,,i-.efore, acts oia a pii-oted cbnt!,c'L o'i the brancli eirevii-ts @oiiipri,-ing tho thei@- II-,it "C ebils 32 2@8 a,,:c, sa prop @oiii@,er ii-l-iieli is 1)ositiol-.ecl to el ' i@@ iet-la - vhe,@ @))i)era'ii , es )se ;ii i I)ositioiis, ai-i ti , t i i tlip- te. at the 'L@,;:o 'Ll,@c 125 @y,--N,ei.,nilig a motor -N-"llich controli iiio etel-s ar@ '- !, sfiiii:e, the ele I-.I e L @C (I a,. ill tile 1)ipe 12. TI-e d,!@,,,,l @,r ,i, i i,-l f oi@-ce,S SCt lll,- by tl-le -@olello-t!,S '-TICI -p il-l(y m6tor @@lue se, Li-,@it Wheii be eqtt,,.tl, ,t@-,d t',,.-ie rosti,.t-',-ncr compo@--le,,-,t of co_,- is (--!tie to a iii tl.,Iose t Ay, f 0 t @.@ c, ,3 '@ATIII be zei-o. Hoivever, a,s ric iii. t', e se,6.11"i @:sta-,-,,- e the@iiio..Ii- the t6inp6rttur6 -at tn@(I tl- -,imoii -tel, 38 '@)e1. illa 0 iii a coines (,,,r L@lle ir@o'coi- 'o(, ota,'L(,' e,,itei- tl)an t@ti,,tt @it tl, thermGmc@to,-c

1,644,123 .'OL9, the resist,,ince throzigh the @Lhermometer 38 iiiereases and a corresponoino-ly sm,,iller clirrent is sent through the s@ieiioid 50 tlilii passes tliioiioh the sbllenoid 44. As a resiilt, r) the electi-ollitigiieti.e foi-ce genei-a'Led by tl)e @@ol.erioicl I@l is g,@-citei- tb,,tt (yenerated I)y the 2-oleiaoid 0-0, and the coi-iil)oi-,eDt (-,i t,iie forces resultip-o@ froi-ii this iinequal excitation of the sole,,ioicis 44 @-,iid 50 acts on a contetc-'u 'O poiiiter 52 to cl@e et tlif,, pointer to the rl(,I-it. 1'e A,s the tempel attire of the thermoiiietei- 38 falls to tllat of the therilloiiieter 32, or i.s bi,otight to ,t tempei-atui-e s'i'l,,o;litly loiver tliaii th at of the tlieriiiometer 32, diie to the aL-- s ence of any co-Liibttstible mpterial in 'Uhe s ample ivithdi-,tvvn from the Pue 18, and to zt sli g@t coolin2@ ,icti.on due to 'L-he iiitrod-Liction of air tlirot.l@li the pipe 26, the resistance ii-i th e eire-Lilt comprisiiig the @Lhermometer 38 - 0 bc,,comes less than that iia the circuit col.-Ilp risinu the thermometer 32. As a result, .t la rger etirrent flovvs tlirotio-li t'iie golenold 50 tlian through tl-ie, solenoid 44 -,Llld, the resi-i'lta nt P-lectrowlignetic -.@orce s-wings the pointer 2,5 to the le'Lt. i\- s the pointer 52 is de@lected to the i-ilf)'Iit 'o r left by the changes in the temperattire of th e tliermometers 32 tnd 38,. it operate-, a c oi-iti@olling mechanism goaerning ,t damper30 to di-ive 'Lhe m operatino, motor otolr in opposite dii@ections. in overni-noltle dirpcticn 9 -otation -r ,iT-ict mot the of i of the damp poiiiter 52 altei,n,-@tely @ollt"tet I-)O1-,weei-i ,i so I urce of electri.c etirrel-it anct one o@,- the otlici- of bi-aiieh circuits o-overlli-ng tn clecti-omagnetic -sivitch. The eiectr6ma"- t, netic svjiteli operates in one positio_n of the pointer ,)9- to close oiie br,@n(,@h of a main electi-].c,, ell-c-Llit ltlii-c-Li-,h oiie of- two oppos40 "I-lo,, i'ie'-il - AA,illclil)gs of ti-i6 (-.Iai -ii-oer-operatiii6'Lor. As the poin@ter@52 s-wi@n-S in the ol@i@(,Site clirec'uioll, 'It o erates the electrop S-',)Titeki @o close the ireiiit tlirougli L c ,(.110 other @'i,@,ld -v@i-,icling of the motor to clrive 45 the i-@iotor --,n the opl)osite direction. In this -1 i,, as 'clic poi.nter 52 silvings back incl coiitro'is 'uhe dampe, -oi)eratii-ig moTO, tor to open o.-7 close t]@ -c daiiipci@ and tl-iereby (,o-lltral the of aii- stipplied throti(,Yh tl-ie air@ stipl)ly pipe 12. I.-i ol)ci-atiii(- the clectrojiiao-n(3ule switch, fl,ii electric current iloivs@ from i battepy 54 fliroliulq q iiit-'Lli 56 'Lo the contac@ pointei, 52. As It@lie conte@et pointer 59- swin,,Ys to tlie' r crh,, it ciia,,io@es "-itli a cont,,ic'L 58 ancl closes ll(,,ciiT-io- fi-oin the contact 53 throuuh ,t 60 lo a 'ole o'd 62 of an electromao@e t, s n i netic s-wi-'Lleii 63. Froill the solenoi-d 62 the etirrent returns tlirough a branch ivire 64 and a maiii returii wire 66 to the bat,tery 54. As Ilh,- solei-iold 6-9 is excited "D-V the currer)t - Trom the, b,,ittery 54, it draws upivtirdly a core 68 ond defl,.,cts a pivotecl leier '@O to ivhich t,ie c6re 68 is coniiectecl at its loiver end. As the lever 70.is deflectecl on ifs pivo"-: 72 COR7 tacts Avith a contact @6 leacling f roi-ii an electric main 't8 and a, contact 80 leadin@- to the daiiiper operated in6tor. Clirrent then flonvs fi-on-i the m,.iiii '@8 throtigli the contac'-, '@6, lever 70 @incl contict 80 to ,L bi-a@ieli eiretilt 82. 1,1'i-oiii the bi,@i3icli circuit 82 tli,-, cui,i@en'. i'lovv,." L f-lel(i windino, 84 (Fig. 1) ai-i-ii,<itiii-e 86 of ,i ii-iotor 88 aiid i-ettiriis tlii,ou,,@li an electric ii-iaiii 90. As the cuiteiit floavs h 'chrou(y the lield wilidin(, 84 aiid the ariiiattii-e 86, the niotor 88 i-otates a clatilpei, '2, by meaiis o-l' a ivoriii 94 and a (Ye@,,r 96, iii a direction to open the damper. The rota@i.on oT- the motol- 88 Lnd dainper 92 is L coiitintied tin'L'Il air sufi@cient f or coi-iiplet.-.- coinbustion is admitted to the ful-nice. I-lv'hop this point is reached the temperatiii,e of thetliei-iiiometer 38 ivill until '@licforces of the sojeiiolds 44 Lincl 50 become eqliil and the poiiiter ,j2 comes to a inid-position or is deflected to the lef L. As the contact pointer 52 is deflected to the left, diie to a cli@op in the temperattire of the theriiiometer 38, con'Lact is made betweelt the conltet I)oiiiter 52 and a contact 98 connected to the electroma(ynetic sivitch 63. A171-ieit th;s contact is made, eiirrei-it froiii the 1,,attery 54 flows thi@ough the ivires 56, pointer )2 an(i contact 98 to a bi-anch circuit 100 I.eactino- to a solenoid 102 o'L the electi-oinq,- c -,titch. Fi,oin the s6lieno'd 102 the etti-@ noti si i,en't- i,etlii,ns throtigh a bi-ancti civctilt 104 and the niain return Nvire 66 to the battery 54. As the solenoid 102 is excited by the current, it dre,,ws ii Nvai,dly a core 106 connected 'Llo p tlie end of the lei,er 'tO opposite that to whicli the core 68 is attached. As the core 106 I'S cl.1-aii,n upnvardly by the solenoicl 102, colit,-,C'C i.s made throtigh the lever '@O bet-ween a contact 108 connected to the main 78 ai-id a coii-, tact 110 leadiny throti(Yli a briiieli eireuit 112 to the motor 88. The etirrent from tlio, branch circuit 112 passes thi-o-ii-h a fie'ld wincling 114 of -'Lhe motor 88 - vvhich is oppo,3itely wolind froin the field ivinclino, 84 an,-l throiigh the armat,,ire 86 to he t eleet@ric main 9,0. As the current pa,sses throuch the fie'llcl windiiig 114 and ariiiatilire 86, it reverses ttie field and rotates the n-iotor 88 in the oppositdirection. When the direction of ro@La'Lioii ot the motor 88 is revei@sed, tlie, d,,tmper 92 is i,otated in the opposite diree't-l'On to el-ose @Llie draft throiigh the pipe 12. The operation of the device is brie'.Iy as -lO s I Ilo-ws: Air for stipportidg coinbu tioii is forced by the fan 10 to the fiirnace 14 at a rate controllecl by the position of the claml)el, 92 in the air suppl@,7 conduit. The prodLicts oi combtistionresultiiig fioli-i the coi,-ibustioii of f Liel in the furnace 14 a,,,e ivithdra-wn througli the flue 18. If the qu,@i-iti' UY Qf air supplied throu(Yll the _conolilit 12 is iiis@Acie-n@ for co'm'p"I'et-e combustion, part of 130 e fuel supplied to the -ftirnace wi I not be

completely burned ard the procl-Licts of coinbust;on passiiig fiom the @(-I,,,ie 18 coiitaiii Liii.bti.i"iied coilibustible gases. A small representati NTe porti--n of the fitie pi-odticts passiDthrough tiie fILie 18 is contii-iiitilly byn -, pags-.CL throu(,,Ii, the shtint tub-. 20 in whi-,hit is mlxecl. -,vith ,tii e--,:cess of the pipe 12 tlrougli tlle bi.@aiieh pipe 1-16. T'ile by-passed fliie ffases and tiie air stipplied tlirotigh the pipe 26 ,tre he,,Lted by the I ). a electi-ic 28 to the -,,itio of -Lbe coiqbiistibles in the flue gases, aiid ,tre biirnecl )- Vhile passiiio@ tl-ii@oti(rh th(, contact (,-auze 30. T'ile rise in tempoi-atur(, of the gases clue to -ombi-Lst;.oi, , detei-:niiiiecl by the el-Ictr4lc tti.ormomeluers 3@-) @inlt 38 i),Iiiclii ,aieasiire tl -ie teii-i,,Dei-aLtii-es of the rir a,,id fltie gas before aiid ,tfter passing throiigh the gauze 30 ' !ATliei-i the prod-Licts of ,,u tion from the furnace 14 contait-i coi iil),,istil),Ic gases the tempe:rattire, ,tiid -@lio resls'u-an-,@e, of the thermoiiieter 'oS become o@reater thaii tl-i.-.t of the theri-noineter 32, cliie to the buriiing of tl"e coiaibus'u-ibles i-ii mixtui-e aitd ,t lai-gei, etirreiat 1),,,sses tl-ii-oiigli the tbermometer 32 ,ind tL@@ coi.1 't-lh,,iii passes throtiyli the thei.,rioi-Doter 38 and the n coil 50. Tile contact I)ointer 5,1@l, is icco,.cl-, deflected to tlae rigl-it and closes the eir3o cuit froi-ii the btttery 51 tlirou,-!,Tl-i the solerold 62. IA7bei-i the cui.@j.@eiit p,,isses ti@rotigli ,iid ei'lergizes the solenoicl CO@, thc,, '@O of thc, el.ectroni,q2@ne'uic sw,,tch 63 is deflecte,-l to coniiect tIAe @-ciciiii '.78 tl-i,@ou(yh tl@ie 35 82 ,tnd field ivid@tihg 84 oT tl-ie i-iiotor 88. The 3-.-,iotor 88 will therotipon be set ip- jiaotion 0 -he iyorm 9z! the 9C) i;iici t i-otate 4. dain])er 92 towards open position. The ciraft fi-om tlie a'r stii)i)',y coi-@diii'u 1-?-, theretipon be sloAAlv iiicreasecl. aiid tli.e ani.oliiit of combustibl@ gases passing tlirough the fiiie Is ivill decre-,isc,,. Wlleii the d@,-@),ft throllt,", tlio, condiiit 19- iiiei-eises to a point at \vhi,-,h the c,)mbiistible gases 4 ed to ,i ppssing tlirough the 'Lliic IS ai@e rediic tl,,e rise in oTgases iipo,.i ],)ei,-ig -,nixed wlth air is reduced @iiat;@l the rc-sist,,iiiees throilgh ttie 32,,ind 38 "Ilncl clrare siibstai-ttitllv equal nd the pointer ci cui @s 5@9, i-P, broiight to its i,,iiddie I)osi:t-'Lon. T.'t-io electromagnetic sivitell 63 is openecl and ctirrent ceases to pass to tl-te moto,- 88 aiid -,otate the d,,tmucl@., 92. The i-e-neter s(@,rves sistance sct tip iii the tlierinoi as a standard of comi)arisoii froiii iihich to meas-Lire the heiting efrect oT-- the blirniii(,r flue gag coiitacted i-vith the-,-,riometer 38. If the s'p ' of air becoiiip-@, too -I the supply uel oiti@, due to a c@eci@a@e i. of f from otlier causes, ',lie teiiip-,r',Lti-ire of tli.e fl-ue g,,ises passi-iig throtigii '6!ie sl@-iui@t pipe 20 will be i-iiieliangecl ii on beiii mixecl p in,ith. the air frqiii the pipe 26, or b;-- may everi be slii)-htly cooled cl -Li.e to asmall 1,644@123 cliftc,,rolice i,,,i the temperatiire of the fltie g,,ises iild tlio ait, frodi tlic ])ipe 26. AccorciiiAgliT, 'Uhe i-esistance It-Ilirotigl-i the the@ ii-io,- noter 3@2, ,,ncl i.ts bi@-,tjicli eire@,ii@t gi-eiteiti).ttn tlic,, res,"stiia,,e t@,ii,oii-la til@,@ t-I 38 "Iiicl i,,@s cori-esi,,oiicii I I I ng cil.- cuit, aii,,l t'ile coiit,-Let poiilu-@,r 2 -,vi'-l be sy@TLi-,ig to the to eolliiect tlle I)atte-e;cs .5,1 -vi-t'll the solonoi.cl 102 o4l' tli(, @A,@Ticeh 63. Ul)oll tb.e pass"tge ol,l clill,,,e-@ik' rli and '- throti,. tl-io e-ioi-gizi.ng r)f ['Ile solei-ioid. 1-02, I'li,e loyc), 70 oi the swite'i.l i,@, to coii,,iect tl it iyi.)in 'TS i-vitli tlio (@ircti-@t 112 ai-id iii,,ic-tin(T 114 of th,@ iiiotol., 88. Ti-ie cl'ii.@ectio-@i of rotatioii of tlio iiiotor 88 aicl woi-iii 91- Is therct)y reve,:s@,,l [lie claii-iper '112 -s rot,,tted loy@-ai-ds clos..-c'L position b-@, the ge,,ir 96. The d@imper 92 contliiues to 'ije sl.O\VIY 1-0- t t e ',-,ho Oraflu- ti-iro P, eci '-o cl@eel-eis the condui-t 12 Lintil the l@ree ox37geT.1 in the 18, Oiie to tl-io ex(@ess of i-s redticecl to a miiiimiim and the poii-iter 52 @.s broiigl-i't-. to its micldle positioii. Ti-I thip, mltiiner thc,, dam-Der 92 is rotate0i op(,,.i oi, close(I positi6n ts the of combtistib.tes iii the flue @ises 'L@l'om i-,I-ie 9 iiice Izi@ iii.el-e-,Ises beyond o,,- f.,ills belo-@-v ,i sjii,,tll Iii-p-itipg qtia,,-@tity. The atialy@is 6f the prodticts of coiiibi-istion by the above device need not be qii,,Lntit,,itii7e, s4lnce it is only necessary to detei@i-iiijie iih,,ther 11 sufrelent' amotint of copib,,isti.l)le (@'ll'ses is present in the producIL-s Of col)lbils11-ioii to iiiove the contact 52 i.nto eii(yao-eiiieiit the coiitact 58 oi@ -",hethei- thei-e is a cl,@,'CiOP-cy 6f combustible stifricient to calise 11 L"tio coiilact 52 to be nioie,li into e.Ti-a(Teme-,ill@ the conta@@@t 98. If tI)c aino-Lin'L of combList'Ll)le g,,is lies witliin these Iiii:iits, it wil't have Do fui,tlier infli7,ence oii 1-.he regulatioi.i o-LI Cie dei7ice. The I)ointer 52 m,,Ly, hoi@7evoi-, be ai:-rangecl to indic,,ti-,e o.Liaiitit,,Ltiiel,7 the @li'10unt of coi-nbiistil)le aases in the fltie ")I.Ocli@,ets by ari-,,tigi.ng it to, siii@,ig past tli-I coi-iI 'I @) I tacts 58 atid 98 aftei@, ii-.taking contact, The time reqi-iii@ed foi- the I-)assa-e of the prod icts of coii-il)ustioii @f-rcm i-lic coi-i@oListio.--- cli,,Lmboi- 14 to the flue 18 througlil the tiibe -90 is ver)r sli.oi-t, beiiig iiiit I t feiv SC(Ilonlls. I ' "i Aiiy chaiige in the i-ate oi, eoiiditions of coil-ibusti-oii i,n t-@he cojilbustioi cliaiiiber 14 i.s tlier,,,fore ii-idicated siibstanti,,tlly ins,-ait,,i,neot@isly b@, the ,in,,tl.yziiig ai,-)p,,ir,,itus in tl-ie tii1a. 20, aiicl the iitotor 88 ig iiistantly S(',t in iii.ot@ioii to ,YradLially but i-apidly cli ii(,,e the a Z-1 positio-.) of the damper 92 to- correspoiid to tho cliingecl conditions in the coiibr,.gti-on chiiiiber i4. The position of the @t,@iiiaper 92 rtiav i,.-,ry froiii closed to ftil@y open p--sii,.ion is the siipply of fi-ilel increases from a smi,lj'. o'i@ practically full load. Whon IL-,he stipply of fi-iel Aaries bet-",een these iiiiii-I'@S. the dainper is ol)eratecl to stipply t@lie miniiiiuin amount of air to insure complete com-

1,644,123 bustio-n of the fuel alicl remains in, this position until an inere,,)se or decrease in the supplv of fuel reqliires that the dailaper be in;ved toiiards a irore open or closed positioii. While the invention h,,is been described iii connection -with a boiler fired -with fluid f-Llel5 it inay be used -witli solid fuel and - with otlier types of furi-iaces. In n-iat-iy types of jo naetallurgical furnaces, stich as are Lisecl for brass iiielting for exaiiiple, it is iiecessary, in order to obtain the reqliii-ed temperature, to use only sufl7icient air to insure coiiiplete combustion, since an excess of air cools the 1,5 flame. and lo-wers the ten-iperature of the ftirnace. When the Pbove described reoulator is Lised, the s-Lipplv of air is Iiiiilted to that which is just necess,,try to insui@e con-iplete, 20 conibustion of the fuel and tl-ie highest possible teiiiperatures inay be obtained. In solaie classes of metallur(,Yical furnices, such as for exainple annealiii furnaces, it is necessary iii order to prevent fla ng an scaling of tl-ie iiietal under tre-,Ltnieiit to 1211) niaintaiii t reducinly atinosphere and to operate with a sligh@t cl@gree of uncler-ventil,,ition and without coiiiplete con-ibiistion, for the reason that any excess of air in -L,he products of combustion has a detrip@iental oxidi7@ing effect on the iNTork@ Accordingly wheii the coinbustionregul,,itor formidthe siibiect of the pi-esent invention is used in co,-iiaec,tion ivitl-i this latter type of furn,,ice, the aiiiolint of air supplied is ii:ept slightly below that which wotild be required to instire colilplete combustioil of the fuel. The regu ltino- device is preferably adjusted so to iiiaii'll@-ain a small limited q-Liantity of co listible in the flue gases during operltion. 40 Other iiieans Tor measurino,- the rise in temperature upon mixing the gases, aiid for controlling the operation of the damper by siieli rise in temperatui,e, iiiay be Lised ill pla,ce of the apparatus specificallydescribed 45 above, -",ithout ITarying the eneral principle o'l. the iiivention. The me-thod and al)paratus of this invention are simil,,tr in certain of their broacier aspects to tl-ie method aiicl apparittis for 50 controlling the combustion of fuel in ,t f Liriiace,- d'selosecl iii my co-pel-idiiig application, Serial No. 358@016) filed Feb. 12, 1920. The subject matter common to this al,)plicatioii and application, Serial N6. 3581016, is 55 claiiiied in tlle latter tpplication. The teriiis " measure " and " measuring " have been used in the specification ,tnd cl,,tims as ueiieric terms to define the essential f-Lincti.01-n@ of a temper,,tttire nieasiL@@rin(, device. 60 iilltmely a theriiiometer. While tl-ie thermomet.ers illustrated diagriiiimatically @ in the accomp@D,nying drawings do not include a showin@,, of auxiliary recordinu apparatus t' for tagiig a visible record o@f the temperac)5 tures measured, it is believecl to be clearly apparent that such recorcling apparattis is not a necessary part of the apparattis forming the subject of the present invention. Accordingly the teriiis ccmeaslire 71 and 44 n-ieasuring' ,is ey are use in t resent 70 case are inteiicled to clefine olily t actual act of temperature naeasureiiient perforiiied bv tl-iemometers, and are not used or intended to define the further step perforined by registerinlr theriiloiiieters, niiiiely that of re- 75 cording the reslilts of said i-iieastiring act in terms of visible conventional readings. Having desci-ibecl the invention, -what is