PROPERTIES OF MATTER IN THE GASEOUS STATE. 
7 29 
Art. Section X.—•Verification of ilie general equation. Page. 
103. Statement of experimental results . . .. .. .. . . . . .. 810 
104-107. Application of the general equation to the transpiration of a gas of uniform texture 817 
108- 108a. Application of the general equation to transpiration arising from varying molecular 
texture .. .. .. . . .. .. .. .. .. .. .. 823 
Section XI.—Application to apertures in thin plates and impulsion. 
109- 110. Equations of motion. Condition of the gas .. . . .. . . .. . . 825 
111. Thermal transpiration through an aperture in a thin plate .. . . . . . . 828 
112-114. Thermal impulsion near a surface. Between two surfaces . . .. .. .. 829 
115. General equation of impulsion. . . . . .. .. . . . . . . . . 833 
Section XII.—Application to the fibre of silh and the radiometer. 
116-118. Corresponding x'esults when the density is proportional to the smallness of the vane. 
Other results . . . . . . . . .. . . . . . . . . . . 834 
119. Author’s earlier conclusions confirmed in so far as they went. . . . . . .. 835 
120. Force depends on the divergence of the lines of flow as well as on the heat com¬ 
municated, figs. 12-14 .. .. .. .. .. .. .. .. 836 
121. Figures indicate the divergence of the lines of flow and the force in the radiometer 838 
122. Stability of the equilibrium . . . . .. . . . . . . . . . . 839 
123. The motion .. .. . . . . .. . . . . .. . . . . . . 839 
124. Other points. Action does not depend on the distance between the hot and cold plates 840 
Section XIII.—Summary and conclusion. 
125-126. General summary . . . . . . . . . . . . . . . . . . . . 840 
127. Dimensional properties of gas. Conclusion . . .. .. .. .. .. 842 
Appendix. 
note. 
1. Uber Thermodiffusion von Gasen (Pogg. ‘ Ann.,’ 1873, p. 302), by W. Feddersen . . 843 
2. On the name “ thermal transpiration ” .. . . .. .. . . . . . . . . 843 
3. Addition to Art. 7. . .. . . . . . . . . .. . . . . . . . . 844 
4. Addition to Arts. 41 and 104 . . . . . . . . . . .. . . . . . . 844 
5. Addition to Art. 119 . . .. . . . . ■ • • ■ . . . . . . .. 844 
PART I.—(EXPERIMENTAL). 
Section I.—Introduction. 
1. The motion of gases through minute channels, such as capillary tubes, porous plugs, 
and apertures in thin plates, has been the subject of much attention during the last 
fifty years. The experimental study of these motions, principally by Graham,* 
resulted in the discovery of several important properties of gases. And it is largely, if 
not mainly, as affording an explanation of these properties that the molecular theory 
has obtained such general credence. 
It does not appear, however, that either the experimental investigations of these 
motions or the theoretical explanations of the properties revealed have hitherto been 
in any sense complete. 
* Edin. Phil. Trans., 1831; Phil. Trans., 1846 and 1863. 
5 A 2 
