on some of the leading doctrines of caloric , &c. 385 
rature, is greater than the mean capacity of the two extremes, 
(that is of the ingredients mixed, ice, cold and boiling water) 
and therefore the thermometric tension will be lessened, and 
its mercury will descend on the scale.* This diminution of 
temperature will cause a corresponding diminution of bulk, 
which affords a complete answer to Mr. Dalton's first and 
only plausible argument, formerly quoted against Dr. Craw- 
ford’s deductions, and the opinions of De Luc. With regard, 
however, to these experiments, of mixing hot and cold water 
to find a mean temperature, there are sufficient difficulties to 
render the result uncertain to 2 or 3 degrees. Hence, nothing 
of moment can safely be inferred from them. 
Concerning sulphuric acid in its various states of dilution, 
I beg to refer the reader to my Essay on the subject, where 
he will find several peculiarities relative to its volume at dif- 
ferent acid strengths, that entirely change its relations to 
caloric. I have not seen these formerly adverted to by any 
chemist. They were evidently unknown to Mr. Dalton. 
Chapter III. 
On the latent heat of different vapours . 
What relation is there between the caloric existing in the 
vapours of different substances, and the temperatures at which 
they respectively acquire the same elastic force ? 
On this subject I am not acquainted with any preceding 
inquiries, though a question of such interest has probably not 
escaped examination. 
* Taking Mr. Dalton’s three numbers as correct : then — ^ 12 ^ — 152 0 . 25. 
But i5o°in the middle are equal to the former mean of the two. Hence, the propo- 
sition in the text is demonstrated. 
