1875.] The Atmospheres of the Planets. 455 
whose most stable combinations would be destroyed by the 
great temperature at the surface, to reunite on ascending 
to the cooler strata, only to be again dissociated on sinking 
towards the surface. 
If, therefore, it were assumed that the surface of Jupiter 
might be so intensely heated as to reach a temperature closely 
approaching a white heat, say 1100°C., an extreme view of 
the possible high temperature of Jupiter would have been 
taken, and the resulting depth for the atmosphere of Jupi- 
ter may be regarded as the maximum present under even 
these conditions. It would only remain, therefore, to frame 
some probable law of the decrease of temperature of 
the atmosphere from the surface, for it is impossible 
that the air could remain throughout at this great 
temperature; but seeing how quickly gases cool under the 
condition they exist under when forming portion of the 
upper strata of the atmosphere, a very rapid degree of 
cooling might be expected when at a little distance from the 
surface. The actual law of decrease of temperature is of 
course unknown but sensibly, except close to the surface; 
the results obtained by employing any approximate law will 
give results sensible the same as the true, for the purpose in 
view here, as well as for most others, including the computa- 
tion of the refraction. In framing such a law it will be 
necessary to put it into such a form that it can be readily 
applied without alteration, not only to different views of the 
conditions prevailing upon any one planet, but to those upon 
the whole six. The temperature of any strata of an atmo- 
sphere must be held to vary in some manner inversely as its 
density, this law regulating implicitly not only the conduction 
but the absorption of heat, as well also as the radiation, 
although not explicitly. It will also be apparent that close 
to the surface the temperature will decrease slowly, owing 
to the influence of the hot surface, and that, from exactly the 
reverse cause, the temperature towards the outer portion of 
the surface will vary with extreme slowness, the quickest 
decrease being in the central portion of the atmosphere of 
any planet. 
Returning to equation (6), assume— 
Oat cieReM Many = case Vue 
where # 1s a new variable introduced to retain the equations 
in a simple form, and such that— 
& pas=(1-f) Paice - “(1—e-") ene (13) 
VOL. VI. (N.S.) 3M 
