240 MEASUREMENT OF HIGH TEMPERATURES. [bull. 5< 
conditions of application deserve most careful scrutiny. I am justifiei 
in believing that the favorable character of the results which this char 
ter contains will be sufficient to show that the transpiration pyromete 
is more than equal to the demands made upon it. Interpreted by th 
Poiseuille-Meyer formula transpiration data must enable us to measur 
temperature absolutely, over a wider thermal range, and with greate 
convenience and accuracy than is now possible with any other instru 
ment. 
An important part of the present chapter is the new light it throw 
on the thermal relations of viscosity and on the thermal relations of th« 
mean free path of the molecule of a perfect gas. The phenomena o 
diffusion, heat conductivity, and viscosity in gases, depending, as the^ 
do, in their thermal relations on the law of force between the molecules 
have hitherto remained beyond the reach even of theory. 
The present chapter is divided into two parts, the first of which con 
tains experiments made with true capillaries. The second part contain! 
experiments with tubes of larger bore— with tubes, in other words 
which do not strictly satisfy the capillary conditions of the Poiseuille 
Meyer law. 
Literature. — The work of the earlier observers has recently beei 
discussed with great thoroughness by Mr. S. W. Holinan 1 in the las 
of his fine treatises on the relation of viscosity of gases and tempera 
ture. Profiting by this, I will therefore dismiss the subject with a fe^ 
cursory remarks, and refer those desiring more specific information t( 
Mr. Holman's researches. Historical reference is also made in O. E 
Meyer's 2 extended article, where the salient features of Graham's 3 classk 
experiments are analyzed. A clear account of the whole question ik 
given by Meyer in his well-known book. 4 
Some years after Graham had published his experimental results 
and after Clausius 5 had pointed out the kinetic importance of the meai 
free path traversed by the gaseous molecule, the questions relating t( 
the viscosity of gases were placed on a new theoretical footing by tut 
remarkable results of Maxwell. 6 Using Stokes's 7 results to treat tin 
viscosity of air, Maxwell is able to express the mean free path of the 
molecule absolutely. The data here in question were derived by Cou 
1 S. W. Holman : Proc. Am. Acad. Arts and Sci., vol. 21, 1886, p. 1 ; Phil. Mag., Lon 
don (5), vol. 21, 1886, p. 199. • 
2 0. E. Meyer: Pogg. Ann., vol. 127, 1866, pp. 253, 353. 
3 Grahara: Philos. Trans. Roy. Soc, London, 1846, p. 573; ibid, 1849, p. 349; Ann 
der Chem. und Pharm., vol. 76, 1850, p. 138. 
4 Die kinetische Theorie der Gase, Breslau, 1877, p. 123. 
5 Clausius: Pogg. Ann., 4th series, vol. 15, 1858, p. 239. 
6 Maxwell: Rept. 295th Meeting Brit. Assoc., 1859 (1860), notices, etc., p. 9; Phil. 
Mag. (4), vol. 19, 1850, p. 19. Less closely allied results in Phil. Mag. (4), vol. 20, 
1860, p. 21. 
7 Stokes : Trans. Cambridge Philos. Soc, vol. 9, 1850, p. 166 ; ibid., vol. 10, 1851, p. 
105. Fortschr der Physik, 1850 : 50 ; p. 101 ; Phil. mag. (4) 1, 1851, p. 337. 
(894) 
