38 SPECIAL RESULTS IN THE UKANOLOGICAL 



Among the many grounds of uncertainty in respect to a 

 numerical result for the thermic condition of space, is the 

 circumstance, that we cannot yet obtain a mean of the points 

 of greatest cold of the two hemispheres, as we are still so 

 little acquainted with the meteorology of the southern hemi- 

 sphere, which must bear its part in determining the mean 

 annual temperature. Poisson's view, that, owing to the un- 

 equal distribution of heat-radiating stars, different regions of 

 space must have a very different temperature, and that, from 

 the movement of the whole solar system, our globe in tra- 

 versing warm and cold regions has received its internal heat 

 from without, ( 75 ) appears to me to have a very low degree 

 of physical probability. 



The question whether the thermal condition of space, 

 or the climates of its several regions, are exposed in the 

 course of long periods of time to great changes of tem- 

 perature, depends principally on the solution of a question 

 proposed and discussed with great animation by Sir William 

 Herschel : viz. are the nebnlse subject to progressive processes 

 of formation, by condensation taking place according to the 

 laws of attraction around one or several nuclei ? If such a 

 condensation of cosmical nebulous matter take place, there 

 must be, in every transition of gaseous or fluid substances to 

 solids, disengagement of heat. ( 76 ) If, according to the latest 

 views, and from the important observations of theEarl of Eosse 

 and Mr. Bond, it becomes probable that all nebulae, even those 

 which have not yet been entirely resolved by the greatest 

 power of optical instruments, are thickly crowded clusters of 

 stars, the belief in this perpetually-arising production of heat 

 will indeed be somewhat shaken. But even small solid bo- 

 dies, seen in telescopes as distinguishable shining points, may 



