j64 Communication cj Heal from Fire, Fa£ls and Experiments* 



effeifts of wind, or a blaft, becomes a<Sivc in carrying off the heat. If flame be merely a hot 

 wind, it will follow that the ftream of a blow-pipe, when ufed to impel the flame and not to 

 excite the fuel, muft probably aH by impelling the ignited vapour with greater force and quan- 

 .ti:y againft bodies, and no otherwife ; and, confequently, that carbonic acid gas, or any other 

 ..ehiflic fluid, will have the fameeffe6l under thefe circumftances as oxygen. The Count found 

 ■-this to be the cafe with thofe very fluids, as well as with atmofpheric air, urging the flame by 

 the blow-pipe, and ufed to fufe the end of a ftick of glafs. It is probable that this refult may 

 .require to be modified, and the experiments varied, in order to reconcile it with the eiFefts pro- 

 duced by the ufe of oxygen, in fufing filex and other incombuftible bodies by Lavoifier, Erhman, 

 and others; but there is no doubt that it is ftrikingly conclufive with regard to the prafti- 

 cal objefl, to which our author applies his reafoning. The boiler 4o be heated t/iuJI not only expofe 

 as large a furface as pojfible to the fame, and hot vapoury but it muji be offuch a form as to caufe 

 .the fame whiJi embraces it to impinge againfi it with force, to break againfi it, and to play over 

 its furface in eddies and whirlpools. It is therefore againft the bottom, and not the fides, that the 

 principal efforts mufl be direfted. 



The next chapter, V. prefents an account of experiments with fire-places and boilers of va- 

 rious forms and dimenfions : a philofophical and practical courfe of unparalleled felicity, whe- 

 ther we confider the abilityand -condudt of the direftor, or the means afforded to perform 

 .them. In order to obtain a refult capable of comparifon, it is taken for granted that equal 

 .quanties of fuel fimilarly expended, will raife the temperature of water through the fame number 

 .of degrees. Whence, by knowing the original temperature and quantity of water, together 

 .with that .of the fuel expended to raife it to the boiling temperature, the refult may be exprefled 

 by flating the quantity of water at 32°, which would have been raifed 180° degrees by lib. of 

 .the fuel in that furnace *. The Count calls this the precife refult^ and fometimes adds the 

 quantity of water which might have been kept boiling one hour by lib. of the fuel ; which lafl, 

 as he remarks, cannot be very exaft. 



From the indifpenfable motive of brevity, it becomes neceflary to refer the reader to the efTay 

 itfelf for the particulars of the refpedtive conftruSions, and the ufeful confequences to which 

 they point. I fhall, therefore, mention fome of the leading fails, and then give the defcriptioa 

 •of the furnace and boiler delineated in the plate. 



The fuel made ufe of was wood ; and it is a fa6l of no inconfiderable value, that pine wood, 

 which, weight for weight, cofls, in mofl places, only half the price of beech, affords more heat in 

 its combuftion. It was not found, as might be expefted, that the faving of fuel was greater the 

 larger the fcale of operation; but, on the contrary, the experiments {hewed that there is a 

 maximum of cffe£t with fmgle fire-places, which will be departed from when the quantities of 

 liquid either exceed or fall Ihort of a certain definite quantity. The caufes of this are pointed 



• lo the form of a rule. Multiply the quantity of water "by tlie number expreffing the degrees aftually raifed; 

 multiply the number of pounds of fuel expended by 180. Divide the firft produft by the latter, and the quo- 

 tient will cxptefs the water which would have been raifed 180° by 1 lb. of the fuel. N. 



out, 



