ASTRONOMY: S. B. NICHOLSON 
147 
These experiments prove that single cadmium atoms actually evap- 
orate off of a glass surface at temperatures below room temperature, 
although they do not do so at an appreciable rate from a cadmium 
surface. 
This theory affords a very satisfactory explanation of Moser's breath 
figures on glass and the pecuHar effects observed in the formation of 
frost crystals on window panes. In fact, the theory appears capable 
of extension to the whole subject of nucleus formation, including, for 
example, the crystallization of supercooled Hquids. 
The final paper will be submitted to the Physical Review for 
publication. 
1 Langmuir, I., Physic. Rev., Ithaca, N. Y., (Ser. 2), 1913, 2, (329-342); Physik. Zs., Leipzig, 
14,1913, (1273); Langmuir and Mackay, P^3'^/c. Rev., Ithaca, N. Y., (Ser.2),4, 1914, (377-386). 
^ Lai.ngmmr, I., J. Amer. Chem. Soc, Easton, Pa., 37y 1915, (1139-1167); J.Ind.Eng. Chem., 
Easton, Pa., 7, 1915, (349-351). 
3 Langmuir, I., Physic. Rev., Ithaca, N. Y., (Ser. 2), 6, 1915, (79-80). 
* Wood, R. W., Phil. Mag., London, 30, 1915, (300-304). 
6 Langmuir, L, Physic. Rev., Ithaca, N. Y., (Ser. 2), 8, 1916, (149). 
6 Langmuir, L, /. Amer. Chem. Soc, Easton, Pa., 38, 1916, (2250-2263). 
7 Langmuir, I., Gen. Electric Rev., Schenectady, N. Y., 19 y 1916, (1060); Philadelphia, J. 
Frank Inst.. 182, 1916, (719). 
> Wood, R. W., Phil. Mag., London, 32, 1916, (364-369). 
9 Barus, C, Ibid., 29, 1890, (150). 
" Langmuir, I., /. Amer. Chem. Soc, Easton, Pa., 38, 1916, (2286). 
THE NINTH SATELLITE OF JUPITER 
By Seth B. Nicholson 
MOUNT WILSON SOLAR OBSERVATORY. CARNEGIE INSTITUTION OF WASHINGTON 
Communicated by G. E. Hale, January 18, 1917 
The Ninth Satellite of Jupiter, whose discovery was announced in 
these Proceedings, 1, 1915, (12), was rediscovered at the Lick Observa- 
tory during the 1915 opposition and the observations secured then were 
forwarded to me before publication. On the basis of these positions the 
preliminary orbit,^ derived from observations in 1914 at the time of 
discovery, was approximately corrected so that the satellite could be 
more easily located at the 1916 opposition. Four images of it have 
been found on plates taken here by Mr. Shapley with the 60-inch re- 
flector. Although the computed position was in error by about 2' 
there can be no doubt as to the identification of the object. 
Observations are now available for three oppositions and the orbit 
is being corrected to satisfy them. Although the final elements will 
differ considerably from those now available, our present knowledge of 
