330 RECORD OF SCIENCE FOR lS«r.. 



ill order to be able to subordinate it to all reversible processes, the 

 speaker bad undertaken some transforuiatious of it, and had introduced 

 into it the conception of the " kinetic potential." In the form it has 

 thus attained, the Hamiltoniau law — the old principle of the actio 

 minima — has in point of fact universal validity. It has just as wide an 

 application as has the law of the conservation of energy and reveals a 

 whole series of mutual relations between the different physical proc- 

 esses. (Nature, July, 188G, xxxiv, 30S.) 



Becker has propounded a theorem of maximum dissipativity, as fol- 

 lows : In all moving systems there is a constant tendency to motions 

 of shorter period. And moreover if there is a sufficient difference be- 

 tween the periods compared, this tendency is always a maximum, so 

 that all natural phenomena occur in such a way as to convert the 

 greatest possible quantity of the energy of sensible motion into heat, or 

 the greatest ])ossible quantity of heat into light, etc, in a given time, 

 provided that the interval of time considered exceeds a certain frac- 

 tion of the period of the most rapidly moving particles of the system. 

 From this it follows immediately that the higher forms of energy can be 

 j)roduced from the lower, or motions of longer period from those of 

 shorter period, only on condition that the sum of the transformations of 

 the system is equivalent to a degradation f a result nearly identical 

 with one of the chief deductions from the second law of thermodynamics. 

 (Am. J. Sci., February, 1886, III, xxxi, 11 o.) 



Tait has undertaken a mathematical investigation upon the jiartition 

 of energy between two systems of colliding spheres, because since 1860, 

 when Clerk Maxwell published his first grand investigation on the sub- 

 ject, it seems to have been taken for granted than in a mixture of great 

 numbers of colliding spherical particles of two kinds, the ultimate state 

 would be one in which the average energy of translation is the same 

 for a sphere of either kind. (Nature, January, 1886, xxxiii, 270.) 



Exner has employed a new method for calculating the size of mole- 

 cules. The Kinetic theory of gases gives the diameter of a molecule 

 as a fraction of the mean length of free path and of the ratio of the 

 space actually occupied by the material particles to their apparent 

 volume. Olausins has obtained this latter value in terms of the dielec- 

 tric constant; and since this is equal to the square of the refractive 

 index, in terms also of this index. Hence, knowing the mean length of 

 free path of the molecules of any gas (determined from diffusion or in- 

 terior friction) and its index of refraction, the actual diameter of the 

 molecules may he calculated. Exner's figures are as follows, expressed 

 in centimeters. They should all be multiplied by 10^ : Air 10, CO2 13, 

 CO 13, n, 10, CH4 12, C, II4 21, NH:, 16, H, O 19, X 17, NO 10, O. 16, 

 H2 S 22, HCe 18, SO2 17, Cca 19, and C2 N2 19. To this table the 

 author has added the relative atomic volumes and relative specific 

 weights of certain substances. By the latter is to be understood the 

 weight in grams of one cul)ic centimeter filled with the molecules on 



