On Dalton's Method of Measuring Water of Crystallization. 207 



gree of heat; and the temperature of the river Niagara will 

 be raised about one-fifth of a degree by its fall of 160 feet. 



Admitting the correctness of the equivalent I have named, 

 it is obvious that the vis viva of the particles of a pound of 

 water at (say) 51°, is equal to the vis viva possessed by a pound 

 of water at 50° plus the vis viva which would be acquired by 

 a weight of 817 lbs. after falling through the perpendicular 

 height of one foot. j buiiow ^ti oJ biit? 



Assuming that the expansion of elastic fltiids oh the r&i 

 moval of pressure is owing to the centrifugal force of revolving 

 atmospheres of electricity, we can easily estimate the absolute 

 quantity of heat in matter. For in an elastic fluid the pres- 

 sure will be proportional to the square of the velocity of the 

 revolving atmospheres ; and the vis viva of the atmospheres 

 will also be proportional to the square of their velocity ; con- 

 sequently the pressure will be proportional to the vis viva. 

 Now the ratio of the pressures of elastic fluids at the tempe- 

 ratures 32° and 33° is 480 : 481, consequently the zero of tenM 

 perature must be 480° below the freezing-point of water. 



We see then what an enormous quantity of vis viva exists 

 in matter. A single pound of water at 60"^ must possess 

 480° + 28°= 508° of heat, in other words, it must possess a vis 

 viva equal to that acquired by a weight of 415036 lbs. after 

 falling through the perpendicular height of one foot. The 

 velocity with which the atmospheres of electricity must revolve 

 in order to present this enormous amount o^ vis viva^ must of 

 course be prodigious, and equal probably to the velocity of 

 light in the planetary space, or to that of an electric discharge 

 as determined by the experiments of Wheatstone. 

 ••-^/■'i I remain, Gentlemen, ^ 



Oak Field, near Manchester, Yours respectfully, 



: August 6, 1845. James P. Joule. 



XXXII. An Examination of Dr. Dalton's Neiio Method of 

 Measurifig the Water of Crystallization contained in dif- 

 ferent varieties of Salts. By Samuel Holker, Bury*. 



THE subject of this paper was suggested to me by my 

 friend Mr. Davies, Professor of Chemistry at the Royal 

 Medical School, with whom I have for some time devoted 

 myself to the study of chemistry. I may observe as a rather 

 remarkable circumstance, that an inquiry of so much interest 

 and importance, commenced by Dr. Dalton, and displaying 



* Read at the Manchester Literary and Philosophical Society, February 

 20, 1844; and communicated by the Author. 



