No. 149.] 185 



low capacity for specific heat. Following out his owu hypothe- 

 tical views, Mr. Frost chooses to call his supposed new combina- 

 tion of aqueous matter and " caloric" by the name of Stame. 

 Your committee are not of opinion that the use of such new name 

 is of absolute necessity, and hare therefore avoided its employ- 

 ment, particularly as the epithet dry^ if applied to steam not in 

 contact with water, is fully and sufficiently expressive of every- 

 thing that is positively known, or which requires to be expressed 

 in language by way of distinction between steam heated out of 

 contact with water, and steam in contact with water whence it 

 has been generated. 



In expressing a difference of opinion from Mr. Frost, in rela- 

 tion to the law of the constancy of the quantity of heat in ordi- 

 nary steam, and in respect to the necessity of a new name for dry 

 steam, your committee do not intend to detract in the least from 

 his liigh merit, nor from the value of the deductions he has made 

 from his experiments. These deductions are of great value as 

 additions to the theory of elastic fluids, and afford an explana- 

 tion of facts and occurrences which no previous theory has reached. 

 We have seen that an increase of the temperature ol dry steam, 

 from 212'^ to 650*^, or little more than 400° increases its elastic 

 force nearly ten fold, and that this increase of force can be at- 

 tained by an expenditure of heat not greater than one-fourth of 

 that by which the steam was originally generated. Can it be 

 doubted that in this simple but hitherto unknown fact lies the 

 cause of by far the greater part of the explosions of steam boil- 

 ers. It is conceded by almost all who are comjDetent to examine 

 the subject, that the dangers which might otherwise accompany 

 the use of steam generated in a boiler no part of whose surface is 

 hotter than the water it contains, can be prevented by the use of 

 the common safety-valve, and the very weakness of parts of a 

 boiler, may prove a source of safety. On the other hand it is al- 

 most always possible to infer that there have been causes capable 

 of heating some portion of the boiler to temperatures far above 

 those of the water it contained, previous to all positive explo- 

 sions. Now if an additional heat of 400° suffices to increase the 

 elastic force of dry steam nearly ten-fold, how great might the 

 increase of elastic force become, if the steam were in contact 



