1876.1 *^^^ [Trowbridge. 



planet seems to be brighter, or to give out more liglit than what it reflects 

 from the Sun, we shall suppose /\ equal to 2. The force of gravity on Ju- 

 piter is about 3.43 times terrestrial gravity ; and if we make some allow- 

 ance for an extensive Jovian atmosphere we may perhaps call g == 2.5. 



If these values be put in Eq. (33), and we make A = ^p, we shall have 



z^ 4- 3rz 

 3.6Zj = — I — ' and z = 1.2z, nearly, ^= 4.1156 miles. 



If we make t^ = we shall find z = 1.3718 miles, or about one-third of 

 the other value. In a similar manner we shall find for the relation A = 4^>, 

 z == 8.2313 miles, and so on. 



If in Equation (19) we make K = 1, and Ato = 2, we shall have A = 2 Aq 

 . . (25) very nearly: Thus at the hight of about 4 miles the density of the 

 Jovian atmosphere will, upon these suppositions, be the same as the den- 

 sity of the Earth's atmosphere at the surface of the Earth. If we suppose, 

 as Mr. R. A. Proctor has done, that the density of Jupiter's atmosphere 

 where the cloud-layers exist, is one-fourth of the density of the Earth's at- 

 mosphere at the Earth's surface, we shall have z for that case about 12 

 miles instead of 100 as he supposes. According to this investigation, then, 

 Jupiter's atmosphere at his surface is either very dense, or its extent is not 

 so great as Mr. Proctor imagines ; or his temperature at the surface is 

 greater than 1000^ Fah. 



We may perhaps reasonably assume A = 2^V ^^ Jupiter, and this value 

 will give the hight of his atmosphere about 306 miles ; and if we suppose 

 A = 2''°f, we shall find z equal to about 83 miles. 



If we call K — 1, to = 980°, X' = -^gVo. g — ^> we shall find, by Eq. 

 (18;, the hight of the barometer on Jupiter 82|^ inches. By Equation (U), 

 we find upon the same suppositions that the pressure to the square inch, of 

 Jupiter's atmosphere on his surface, is equal to 93^ pounds. 



If we take for Saturn g = 1.1, /Xq =: 3, A = 2,n> we shall find z = 9.3537 

 miles ; and for A = S^V' ^ — ^^'^ ^^^^^ ' ^^^^ ^^^ A = S^"/'- z = 468 miles. 

 If we take K = 1, Eq. (19) gives A = I Ao- ^.nd the pressure to the square 

 inch equals 18 pounds. The hight of the barometer by Eq. (18) equals 36 

 inches. 



To make some application to the Sun, I shall assume /i.t^ =: 49, wliich 

 will give a temperature of the Sun's surface sufficiently high to correspond 

 with our knowledge of the subject. We also have g equal to 27.2 ; and if 

 A = 2^ we find z =i 6.304 miles. If we suppose A = 2'°*"'^), we shall have 

 z = 6304 miles as the corresponding hight of the solar atmosphere. We 

 also find A = 15 Ao ^^ry nearly, if K = 1 ; and the pressure to the square 

 inch is about 11000 pounds. The hight of the barometer would be 234.6 

 feet. 



In these applications we have assumed K =r 1 which supposes the mass 

 of the atmosphere proportional to the mass of the planet which it surrounds. 

 In the absence of all real knowledge on the subject we may as well make 

 that assumption as any. The probability is that this supposition is an ap- 



