I ON THE HEAT EVOLVED 



was, in every instance, directly proportional to the results- 

 which had been formerly obtained. 



The experiments to determine the comparative loss of heat 

 sustained by using apparatus of different constructions for the 

 combustion of fuel, appeared to be equally necessary with 

 those to determine its comparative efficiency. 



To Professors Hare and Patterson of the University of 

 Pennsylvania, I am under obligations for their kind assistance 

 in my experiments, and it gives me great pleasure to have an 

 opportunity thus publicly to tender them my acknowledg- 

 ments. 



The importance of those experiments, which have for their 

 object the promotion of the useful arts and sciences, or an 

 improvement in the domestic economy of society, by which 

 our comforts may be increased, is generally admitted. 



In a climate like that of the United States, where, during 

 two-thirds of the year, fires are indispensable to human com- 

 fort, and where, consequently, the savings of a large portion 

 of the poor, during the summer, are often inadequate to pur- 

 chase a sufficient supply of fuel for the winter; it must, obvi- 

 ously, be highly important to ascertain, the comparative effi- 

 ciency of different kinds of fuel; as, without this knowledge, 

 those who are desirous of economising, may be prodigal through 

 ignorance. 



The knowledge of the comparative heat disengaged in the 

 combustion of the different varieties of wood and coal, is also 

 important in various processes in the arts, and it is believed 

 that the results of my experiments will be found worthy of 

 attention, in a philosophical point of view. 



Previous to describing my apparatus or experiments, it will 

 be proper to notice those of some of my predecessors, as, in 

 the investigation of this subject, no small degree of inaccuracy 

 appears to have prevailed, even among experimenters of high 

 character. 



My remarks cannot be better prefaced, than by making use 

 of the following extract from Dr. Ure, on the subject of com- 

 bustion. 



