^•406 Mr, Heiififtatk'QH the CauseSf Laws, and principal [JuNt, 



Biithraetical mean. Such a difference as this would be extremely 

 striking and decisive ; but whether those extreme temperatures 

 can be operated on, I leave others to determine. Other circum- 

 •»«tances being alike, the most advantageous method of making 

 the experiment is when the volumes mixed together are equal. 



In any homogeneous fluids the same principles will enable us 

 to discover the ratios of the numeratoms and the magnitudes of 

 the particles. On the supposition that mercury and water are 

 homogeneous fluids, I have found, from the best experiments I 

 can procure, that the ratio of the numeratoms of mercury and 

 •water is about equal to that of 1 to 2, and the ratio of the mag- 

 nitudes of the particles equal to about that of 27 to 1, and, 

 therefore, the ratio of their diameters, supposing them similar, 

 about that of 3 to 1. This greater numeratom of the water is 

 indicated by the mean temperature of the mixture of equal parts 

 of mercury and water always being in favour of the temperature 

 of the water ; and the excess of magnitude in the particles of 

 -mercury, by its less disposition to be affected in volume by 

 fchan^es of temperature. 



\' Taking these numbers for correct, I find that if a given 

 'Volume of mercury at the temperature of lOO'^ Fahrenheit be 

 mixed with an equal volume of water at the temperature of 40®, 

 the temperature of the mixture should be 59-^°; by Dr. Henry, it 

 is 60°. And if the same temperatures be taken, but the water 

 be put at the higher, and the mercury at the lower temperature, 

 the mixture should be at 79-i° : Dr. Henry says it is nearly 80°. 

 If two volumes of mercury and one of water be mixed at the 

 temperatures of 100° and 40°, it matters not whichever of them 

 has the higher temperature, the temperature of the mixture 

 ought to be about 69-^°: by the above author, it is 70°. An 

 equal coincidence holds good in the other cases mentioned by 

 Dr. Henry. Therefore, what has been usually attributed to "the 

 •capacity of bodies for caloric," appears to be explicable on the 

 theory of their numeratoms, that body whose particles are the 

 smaller and more numerous, being that which has been supposed 

 to have the greater *^ capacity for caloric ; " and vice versa. But 

 -to be more certain of this, it would be necessary to make fresh 

 .experiments with a greater difference of temperature. Suppos- 

 ing the aforesaid ratio of the numeratoms to be right, and that 

 ivater and mercury are homogeneous fluids, I find, if equal parts 

 of mercury and water are brought to the temperatures of 40° 

 and 212°, and then mixed together, the resulting temperature 

 should be 151^°, when the water has the higher temperature, 

 and 944-° when it has the lower. The arithmetical mean of 212° 

 and 40° is 126°, which is 31i° above 94^°, and only 254-° 

 below 1514°. If the temperat'ires be 40° and 200°, the mixtures 

 will be 91° and 144°, in which the distances from the mean are 

 — 29 and -1-24. I have not tried these experiments for the 

 reasons I have given before, but I would thank any one who 

 would ; and should be still more obliged to him if he would htkve 



