248 MEMOIR OF DR. D ALTON, AND 



some of his earlier conclusions, having found that he formed 

 laws too hastily. At page 9 of his " New System," he 

 says, " Sometime ago it occurred to me as probable, that 

 water and mercury, notwithstanding their apparent diversity, 

 actually expand by the same law, and that the quantity of 

 expansion is as the square of the temperature from their 

 respective freezing points. Water very nearly accords with 

 this law according to the present scale of temperature, and 

 the little deviation observable is exactly of the sort that ought 

 to exist, from the known error of the equal division of the 

 mercurial scale. By prosecuting this inquiry, I found that 

 the mercurial and water scales divided according to the 

 principles just mentioned, would perfectly accord as far as 

 they were comparable ; and that the law will probably extend 

 to all other pure liquids; but not to heterogeneous compounds, 

 as liquid solutions of salts." 



In Vol. II.* he says, " The great deviation of the scales 

 between the temperatures of freezing water and freezing 

 mercury is sufficient to show, as Dulong and Petit have 

 observed, that their coincidence is only partial :" and so 

 acknowledges his error. 



In the first volume f he also said, that "the force of steam 

 from pure liquids, as water, ether, &c., constitutes a geome- 

 trical progression to increments of temperature in arithmetical 

 progression." Also, "that the expansion of permanent elastic 

 fluids is in geometrical progression to equal increments of 

 temperature." Again,J "that the force of steam in contact 

 with water, increases accurately in geometrical progression to 

 equal increments of temperature, provided these increments 

 are measured by a thermometer of water or mercury." This 

 seemed an ingenious group of laws, and although he gave 

 them up, yielding to the results of Dulong, he published 

 them unaltered in the edition or reprint of 1642. But that 



• Page 289. f Page 13. J Page 11. 



