452 The Atmospheres of the Planets. [October,, 
where the decrease of temperature must be so slight as to 
approach very closely to this condition. This condition is, in 
fact, as far as any of the planets of the solar system are 
concerned, the limit on this side to any possible constitution 
an atmosphere can possess; and as it reduces the equa- 
tions to their simplest form for the purpose of ascertaining 
the extreme in this direction, this condition may first be 
supposed to hold. 
Assuming that the temperature is constant and equal to 
t, then @’ (s) becomes unity and @ (s)=s, whence substitu- 
ting these values in equations (8) and (9), the two equations 
become identical and can be expressed as— 
h = 6 ae efor as (Io): 
po —, Oo o ° ° e 
For atmospheric air it has been ascertained that— 
pi C20 ee (11) 
I-+e to 
and for any other gas it can be found by dividing this by the 
specific gravity relative to air of the gas in question. Com- 
puting the value of the coefficient of s for the six planets, 
Mercury, Venus, Mars, Jupiter, Saturn, and Uranus, and 
denoting by T the quantity 1+¢¢, then the coefficient. 
8 T-tofs on the six planets will be, on— 
Mercury 8 I-?. = o:o086 . Ts" 
Venus Fe = o0672 .. Tes 
Mars ‘5 = 0°0246 . T-* 
and on— 
Jupiter (6hT>2 i= 290). 
Saturn es =) 0800 | ela 
Uranus ,, Ona A At earns 
The planet Neptune has been omitted from its great 
resemblance to Uranus, which renders the physical condi- 
tions regulating the atmospheres of the two planets almost 
identical. 
The length in miles of a unit of s on the different planets 
has, for convenience, been taken so that units of s will, in 
miles, on— 
Mercury = o'148 + 0°00002 n? 
Venus = 0376" + o'00004 n* 
Mars = 0'246” + 000003 n* 
whilst as on the larger planets the second term will be 
always insensible, it may be considered that on— 
Jupiter = 4°30 ”- miles: 
Saturn = 3°60” -miles. 
Uranus = 1°65” miles. 
