No. 149.] 205 



unseen and unknown to engineers cannot be estimated of less 

 value in New- York alone, than the power that fifty croton rivers 

 (devoted to that sole purpose) could furnish during half tlie year, 

 and this costless force would continually increase with increasing 

 population, and thus the onerous expense for fuel may be con- 

 verted into active, comfortable, and lucrative employment for 

 thousands who now languish in uselessness and wretchedness du- 

 ring the tedious wintry months. 



Mr. Frost had a working model in the room, and gave actual 

 experiments of the propositions which he advanced. 



In September last a committee of the American Institute made 

 a report (written by Prof. Renwick) upon the discoveries of Mr. 

 Trost. The conclusions of that report are in the main favorable 

 to Mr. F. 



Having seen the thermometrical degrees at which steam, apart 

 from water, is expanded by heat into larger volumes, it becomes 

 important to learn tlie actual quantity of heat required for each 

 expansion, and the apparatus represented by the lecturer's dia- 

 gram, will show, first, how small is the quantity of heat requir- 

 ed for doubling a volume of steam apart from water, when com- 

 pared with the quantity of heat required for forming a second 

 volume of steam of same tension ; and, secondly, shows that heat 

 in combining with steam is subject to and controlled by peculiar 

 laws, perfectly distinct from those which obtain when heat com- 

 bines with water for the formation of steam, which requires equal 

 increments of heat for equal increments of volume, while on the 

 contrary, when steam apart from water is expanded by heat, it 

 is not only doubled in volume by a comparative trivial quantity 

 of heat, but every additional increase of volume is obtained by 

 a still smaller and rapidly decreasing increment of heat, so that 

 the greater the decrease of volume the smaller will be the quan- 

 tity of heat required for that latest volume, and although this is 

 so contrary to the general laws of heat, and therefore so adverse 

 te common apprehension, the diagram and table will not only 

 show it to be a chemical fact, but will furnish the easy means for 

 any competent person to verify the fact, which must be acknow- 

 ledged to be of the first importance, for, were these facts under- 



