THE SUN'S WORK. 353 



sun-spots. A table drawn up by Mr. Loomis, without suspectino- their 

 remarkable coincidence, establishes it beyond a doubt. 



Nor is this all. Once started on the road, empiric science follows 

 the clew of its deductions. After the aurorse boreales come the cirri 

 the mare's-tail clouds, of a peculiar form, which float very hio-h in 

 the atmosphere, entirely formed of extremely minute spicules of ice. 

 These have an intimate connection with auroras boreales, and seem to 

 be in some sort the atmospheric substratum or stage of all their mani- 

 festations. It is now endeavored to ascertain whether there does not 

 also exist some relation between the fi-equency of those clouds and 

 that of the solar spots. In short, there is now, in meteorology, an 

 emulation of discoveries based on these analogies of periods or on the 

 influence of the solar rotation. And we are bound to call attention to 

 this novel tendency of astronomical research, which Donati, a few days 

 before his death, characterized as the advent of a cosmic meteor- 

 ology that is, as already stated, of a meteorology in which account 

 should be taken of the multiple reactions of the stars on each other, 

 without limiting those reactions to the habitual forces of attraction 

 and heat. 



To this cosmic meteorology evidently belongs Fourier's notion of 

 a combined action which the universe (leaving the Sun out of the 

 question) exercises upon us by its calorific radiations. If the Sun 

 were to go out, the temperature of the solar system would not sink 

 indefinitely or rather it would not fall to the absolute zero (273 

 Centigrade) but would stop at a certain point, which Fourier esti- 

 mated at 62 Centigrade below the freezing-point of water. The im- 

 portance of this temperature must not be estimated by the abnormal 

 figures which measure it : for it appears to be a condition of our very 

 existence, by imposing a limit to the lowerings of temperature pro- 

 duced by the long nocturnal radiation of polar regions. It must be 

 added that Messers. Huggins and Stone have recently justified this 

 bold conception by measuring the heat radiation of several bright 

 stars which they find superior to that of the Moon herself who 

 ought, one would at first sight believe, to reflect so fair a share of 

 solar heat. 



This, then, is the Sun's work. He controls the compass ; he mar- 

 shals the northern lights ; he permits or forbids ice-crystal clouds to 

 hover high in the atmosphere ; besides performing other offices which 

 we may not at present even suspect. And thus a deeper study of his 

 nature and action tends to modify notably the face of Science, to en- 

 large our views, and to demonstrate more clearly by what multitudi- 

 nous links terrestrial existences are connected with the entire uni- 

 verse. All the Year Round. 



VOL. VII. 23 



