53 
Steam Engine* 
particular construction, which, whth the same quantity of 
fuel, and without any increase of expence in other things, 
shall produce an effect far superior to what is obtained 
from the steam of water. Another use of these research- 
es suggested by M. Bettancourt is, to measure the height 
of mountains by means of a thermometer immersed in 
boiling water ; which he thinks may be done with a preci- 
sion equal, if not superior, to that of the barometer. But 
this, being foreign to our present enquiries, cannot be en- 
tered upon here : a comparison of the results of this me- 
thod with some deduced from the more customary process 
may be seen in Dr. Hutton’s Dictionary, vol. IL pa. 756, 
to which such as are desirous of further information on 
this point are referred. 
Our ingenious countryman Mr. Dalton, of Manchester, 
is of opinion that M. Bettancourt’s deductions are not 
quite accurate. His chief error consists in having assum- 
ed the force of vapour from water of 32*^ (Fahrenheit) to 
be nothing ; which makes his numbers essentially wrong 
at that point and in all the lov/er parts of the scale : and in 
the higher part, or that which is above 212^, the force is 
determined too much ; owing as Mr. Dalton appreheiids, 
to a quantity of air, wiiich being disengaged from the wa- 
ter by heat and mixing with the steam, increases the elas- 
ticity. 
Mr. Dalton’s first experiments with spirit of wine led 
him to adopt the same conclusion as M. Bettancourt, with 
respect to the constant ratio between the force of the va- 
pour from this spirit and that from water ; and inferred 
the same with regard to the vapour from other fluids. 
But, on pursuing the subject, he concluded that this prin- 
ciple was not true, either with respect to spirit of wine or 
any other liquid. His experiments upon six different li- 
quids agree in establishing as a general law, ‘‘ That the 
variation of the force of vapour from all liquids is the 
