1842.] THE NATIONAL INSTITUTION. 165 



COIMMUNICATIONS TO THE INSTITUTION. 



ON THE PRACTICAL DETERMINATION OF THE HEATING POWER 

 OF FUEL,: BY WALTER R.JOHNSON. 



In the progress of improvements in arts, navigation, and the application of heat 

 to domestic purposes, questions of great interest present themselves for expsri. 

 mental determination. 



The new era in our Naval history which is about to commence with the intro- 

 duction of war steamers, is a very suitable period to inquire into the relative values 

 of those varieties of fuel which may be found available for the purposes of steam 

 navigation. 



In various parts of the United States are found combustibles adapted to this 

 purpose ; but as yet their relative values, either as compared with each other or with 

 the foreign mineral fuel so much used at present, have been but partially deter- 

 mined. 



In a work recently published relating to the use of anthracite in the manufao- 

 ture of iron, I have given several tables of experiments conducted by different 

 individuals, exhibiting the results of trials on a few varieties of anthracite and bitu. 

 minous coals. The same work also contains a synopsis of what has been done in 

 Europe towards determining this important question of the relative values of coals 

 for the production of steam. 



It is proposed in this communication to present to the National Institution soma 

 few general results, to which the details contained in the above mentioned work ap. 

 pear to lead, and also to embrace a comparison with other results obtained with the 

 same kinds of fuel. 



It may not be amiss to state that the method of determining the relative value 

 of combustibles for the purpose of generating steam, consists in ascertaining the 

 weight of water which can be converted into vapor by the combustion of a given 

 weight of each variety of fuel. 



The method wliich has been often heretofore pursued, "consisted in ascertaining 

 the amount of the ultimate constituents of fuel, carbon, hydrogen, and oxygen, and 

 computing the quantity of oxygen required to enter into combination in order to 

 effect their complete combustion. Assuming that the quantity of heat afforded was 

 directly proportionate to the quantity of oxygen consumed, the calculation of relative 

 heating powers was made upon the admission, that the heating power of pure car. 

 bon had been determined, and that the power of other combustibles would be pro- 

 portionatc to the several quantities of oxygen which they would absorb. 



The experiments of Lavoisier, and more recently those of Despretz, have been 

 relied on to give the heating power of pure charcoal. The latter fixed the quanti. 

 ty of water evaporated by the combustion of one pound of pure charcoal, obtained by 



