1819.| Philosophical Transactions for 1818, Part II. 217 
pains to make mine as correct as possible, and I paid him a 
high price for it. A, 
The second topic which Dr. Ure discusses in this paper, is 
Mr. Dalton’s opinion that the common thermometer is an inac- 
curate measurer of heat, and that mereury and all liquids expand 
as the square of the temperature, reckoning from the freezing 
point. It is not necessary to give a particular detail of the facts 
contained in this part, as, Mr. Dalton’s opinions on this subject 
had been already overturned by the experiments of Dulong and 
Petit.* Dr. Ure’s notion that the capacity of bodies for heat 
diminishes as the temperature increases, is directly contrary to 
the results of the experiments of Dulong and Petit on the sub- 
ject. It seems also contrary to analogy in other cases. We 
know that the capacity of elastic fluids increases as they become 
rarer, and that the rarest of all the elastic fluids has the greatest 
capacity. It is reasonable, I think, that this should be the case; 
for the further the particles of a body are removed from each 
other, the greater must the quantity of heat be which shall be 
capable of producing a given effect on it. 
{n the third part of this paper, Dr. Ure gives usa set of expe- 
riments made to determine the latent heat of the vapours of 
several liquids. He put 200 gr. of the liquid, the latent heat of 
whose vapour was to be determined into a small retort with a 
very short neck. The neck entered into a glass globe, which 
was surrounded by a considerable quantity of water. The latent 
heat was determined by the degree of heat communicated to the 
water surrounding the globe. It is obvious that the latent heats 
determined in this way must be considerably below the truth. 
The method contrived by Count Rumford seems to me a good 
deal better. He cooled the water surrounding the globe 4° 
below the temperature of the room, and continued the distilla- 
tion till the temperature of the water was exactly 4° above that of 
the room. During the first half of the process, the water was 
receiving heat from the air of the room; during the second half, 
it was giving out heat to the air of the room, and the one quan- 
tity must have been exactly counterbalanced by the other. 
Count Rumford found the latent heat of steam and the vapour of 
alcohol as follows : 
BARBI. nrveitiens seeigls she de iptinpyectre sige ep 040:8° 
Vapour of alcohol between........ 477-0 and 500° 
The result of Dr. Ure’s experiments is as follows : 
| Aegan ZAI 6 OP 967-000° 
memour Of HlOONO! se ease tees ke -++- 442-000 
BUNDY ERRER + 5 ott... svins eons. Claes 
* The commencement of their important paper will be found in the last | 
wumber of the Annals, p. 112. 
