84 Prof. L. Boltzmann on some Questions 



paper ? Again, how can Prof. Tait say, on page 255, " I 

 have not yet seen any attempt to prove that two sets of par- 

 ticles which have no internal collisions tend to the state 

 assumed by Prof. Boltzmann," after he has not said one word 

 in actual refutation of my proof, and in the Philosophical 

 Magazine even admits its correctness, no doubt without 

 having read it. But this seems to be the usual habit of my 

 illustrious critic, not to read the works of those authors upon 

 which he sits in judgment. Only in this way can we explain 

 why he has given (on page 260 of his second paper) as new the 

 same formula for the coefficient of friction which I have ob- 

 tained essentially in the same way as Prof. Tait, in my treatise 

 " On the Theory of Gaseous Friction," part ii."*, and have given 

 as formula (9), page 45; the coefficient of B in the expression 

 which Prof. Tait gives in line 14 of the page quoted is the 

 coefficient of friction. If in this coefficient we substitute for 

 Ci the value given by Prof. Tait on page 257 and replace the 

 letters P and s by m and 8 respectively, we obtain precisely 

 my formula (9). Of course, my formula (8) on page 44 a!>o 

 agrees exactly with the value found by Prof. Tait on page 73 of 

 his first paper for ev, which moreover 0. E. Meyer had already 

 calculated before me. 



If Prof. Tait had read my paper he might also have spared 

 himself the trouble of the numerical evaluation of the definite 

 integral, since I have alread} r given (in the formula (9) 

 quoted) the numerical value Ci : 37r = 0088942 6" : whence by 

 multiplication by 37r = 9*42478 we obtain exactly Tail's value 

 Cj = 0*838, only that I have attempted greater accuracy. 



If, in the same place, I have not treated diffusion and con- 

 duction of heat according to the same method which Prof. 

 Tait has adopted, this is simply partly because the calculations 

 in question can be easily effected without this in the same 

 form ; partly because, as I have shown both in the passage 

 referred to and in the first part of my "Theory of Gaseous 

 Friction,-" f at the beginning of the first section, this method 

 does not yield that which at first sight it seems to yield. In 

 this expression (first calculated by me) for the coefficient of 

 friction, exactly as in the older expressions of Maxwell, trims 

 of the same order of magnitude as those giving the result are 

 neglected, and it is therefore not possible to tell whether one 

 comes closer to the truth than the other. 



This also appears in the great uncertainty of the results to 

 which this method leads. E. Meyer, in his book ' The Kinetic 

 Theory of Gases ' (Breslau, 1877), has already followed a line 

 of thought essentially similar, although somewhat more tedious, 



* Boltzmann, Wien. Sitzber. vol. lxxxiv. p. 40 (1881). 

 t Ibid. vol. lxxxi. p. 117 (1880). 



