158 On the Contraction of Water hj Heat. 



in the capacity of the thermometer-shaped apparatus em" 

 ployed, must occasion on the apparent volume of the fluid. 

 lie stated, in general terms, that on subjecting water to 

 different degrees of temperature, in instruments made of 

 different materials, he found the point of greatest density 

 was indicated at a different temperature in each, 



Iti an apparatus, having a ball of earthen ware, it was at 

 the 34th degree ; of glass at the 42d ; of brass at the 46th ; 

 and of lead at the 50th. And as water could not follow a 

 different law, according tathe nature of the substance of 

 the instrument, he conceived that the appearance of ano- 

 maly in this fluid originated entu-ely in the containing ves- 

 sel, which must cause the fluid in the stem to fall or rise 

 .according as its expansions are greater or less than those of 

 the included liquor. 



A detail of these important experiments has, ere now, 

 hcvAi transmitted for publication in the Journals of the Royal 

 Institution of London. 



I have already noticed that Dr. Hooke endeavoured to 

 explain in the same manner t!ie original experiment of Dr. 

 Croune. This explanation apparently gathers much force 

 from these experiments of Mr. Dalton. 



It is proper, however, to state, that M. de Luc was per- 

 fectly aware of the alteration in the dimensions of his glass 

 apparatus, but deemed tlie change too trifling to have any 

 material influence. 



Sir Charles Blagden paid greater attention to the circum- 

 stance, and by calculation attempted to appreciate what 

 allowance ought to be made for the change of capacity in 

 the amount of the apparent changci of volume. 



When it is considered that the whole amount of the ap- 

 parent change is but very small, and that the expansibility 

 of the glass is with difficulty ascertained, and is variable by 

 reason of the fluctuating proportions of its heterogeneous 

 constituents, it must be acknowledged that precision in such 

 a calculation cannot possibly be attained, and can scarcely 

 he approached. On this account, all the experiments al- 

 ready noticed are open to the explanation of Dr. Hooke, 

 and in some measurs liable to the objection which he had 

 iirtred. I confess that the experirneuts of Mr. Dalton, in 

 perfect concurrence with that explanation, created consi- 

 derable doubts respecting the existence of the peculiarity of 

 water; against the probability of which circumstance, all 

 analogical reasoning, and every argument a priori, strongly 

 militate. 



■'Unwilling to remain in uncertainfv, and considering it 

 ^7 as 



