308 Mr. Herapath on True Temperature, and the [Nov. 



then be found that the greater quantity, though it has the same eva- 

 poration superficies, will evaporate more in a given time than the 

 less. This has actually been observed to be the case ; for when 

 equal surfaces of water are exposed under the same circumstances 

 in vessels of unequal depths, that in the deeper vessel usually 

 loses in a certain time more water by evaporation than the other. 



Prop. IX. Theor. VII. 



If any two portions of the same vapour be confined in vacuo 

 over equal condensing surfaces, I say that the increments of 

 condensation, or the little quantities condensed in any small 

 particle of time, the temperatures being the same, are as the 

 elasticities of the vapour. 



I do not here inquire into the particular manner in which the 

 particles of the vapour strike those of the fluid to condense; but 

 the means of condensation, that is, the temperature at the times 

 of the collisions being the same, the probability of condensation, 

 <vr of striking in the particular manner to condense in ihe same 

 particle, is evidently as the number of times of its striking the 

 condensing surface in a given time ; and in two systems of par- 

 ticles, the probabilities of condensation are as the numbers that 

 strike in the same time. But it is plain these probabilities must, 

 considered generally, be proportional to the condensations. 

 Therefore, the condensations in any small particle of time, from 

 two portions of the same vapour, the temperatures being the 

 same, are proportional to the numbers of the particles which come 

 in contact with the condensing surface during that time. 



This being granted, let us imagine the two vaporous media 

 divided into strata parallel to the condensing surfaces, in such a 

 manner that if the particles in each strata were uniformly distri- 

 buted throughout their respective spaces, the corresponding 

 strata in each should be one, two, or the same number of parti- 

 cles thick. Then since the particles of the media and also of the 

 condensing fluids are respectively equal and similar, and the 

 only difference in the media is in point of megethmerin, it is the 

 same as if one medium was dilated or compressed until its 

 megethmerin be equal to that of the other ; and, consequently, 

 the paths of corresponding particles are similar in both. Hence, 

 therefore, the numbers of times the condensing surfaces are 

 struck in a given time by the particles of the first strata, are in a 

 ratio compounded of the ratio of the arithmeridones and the 

 ratio of the number of returns of corresponding particles in the 

 two strata. But these numbers of times are as the probabilities 

 of condensation, and, therefore, as the increments of condensa- 

 tion from the given strata. The strata being the same number of 

 particles thick, and the condensing superficies being equal, the 

 ratio of the arithmeridones is equal to that of the duplisubtripli- 

 cate of the megethmerins. And because the velocities are equal, 

 the ratio of the number of returns will be equal to the inverse of 



