U4 PETER GUTHRIE TAIT 



conclusions ; but he could not admit the validity of all his demonstrations. 

 If we may judge from a letter written to him by Maxwell as early as 

 August 1873, Tait had been seeking enlightenment years before he himself 

 thought of tackling the problem. Maxwell's letter consists of a set of 

 numbered paragraphs, i, 3, 7, 5, evidently in answer to a set of corresponding 

 questions put by Tait. Paragraph (5) runs thus : 



" By the study of Boltzmann I have been unable to understand him. He could 

 not understand me on account of my shortness, and his length was and is an equal 

 stumbling-block to me. Hence I am very much inclined to join the glorious company 

 of supplanters and to put the whole business in about six lines." 



Maxwell then gave the conclusion of his paper on the Final State of 

 a System of Molecules in motion subject to forces of any kind (Nature, 

 Vol. vin, 1873: Scientific Papers, Vol. n, pp. 351-4) and continued: 



" In thermal language Temperature uniform in spite of crowding to one side 

 by forces. Molecular volume of all gases equal. Equilibrium of mixed gases follows 

 Dalton's Law of each gas acting as vacuum to the rest (in fact it acts as vacuum to 

 itself also). In my former treatise I got these results only by way of conclusions. 

 Now they come out before any assumption is made as to the law of action between 

 molecules." 



A few months later (Dec. i, 1873) Maxwell returned to the subject 

 evidently in reply again to Tait. This letter of Maxwell's touches upon a 

 great variety of points, all in reference to Tail's varied activities at the time ; 

 and it seems better to give the letter here as a whole with footnote eluci- 

 dations than to break it up into bits distributed throughout the volume. 



Natural Sciences Tripos, i Dec. 1873. 

 O T'. For the flow of a liquid in a tube 1 , axis z 



dp 



= 



Surface condition fj,-^- = \w .................................... (2), 



where v is the normal drawn towards the liquid. When the curvature is small, 

 (2) is equivalent to supposing the walls to be removed back by /t/X and then X made 

 oo or w = o. For glass and water by Helmholtz and Pietrowski /*/X = o. 

 If so, and if the value of w is C(i x^/a? 



~l + 7i)+p =o > which gives C. 



1 See Tait's Laboratory Notes (Proc. J?. S. E. vui, p. 208) : On the Flow of Water through 

 fine Tubes. The experiments were made by C. Michie Smith and myself with tubes of 

 circular and elliptic bore. Tait had asked Maxwell to give him the theory of the phenomenon 

 as a problem in viscosity. 



