542 THE POPULAR SCIENCE MONTHLY, 



The darkest parts are far from being black, however they may ap- 

 pear by contrast, the very "blackest" part being radiant with a light 

 which would appear intolerable to the unshielded eye. Brown and 

 reddish tints are occasionally seen here with the polarizing eye-piece. 

 These, the spectroscope shows, are due to incandescent hydrogen ; but 

 a common tint, which is particularly that of the nuclei or deeper um- 

 bral shades, is a very pure violet. 



It is impossible to do more, in such an article as this, than to out- 

 line, in the briefest way, a few of the more prominent appearances of 

 the spots and solar surface, without attempting any description of the 

 laws which regulate their respective motions, and the emission of their 

 light and heat, and without alluding to the numerous other topics of 

 interest to the student. The reader will not, it may be hoped, on this 

 account derive the impression that his attention has been invited to a 

 description of superficial solar phenomena, merely as spectacles. In 

 'this point of view alone, certainly, we cannot contemplate them with- 

 out lively wonder, but their deeper interest will lie in the light they 

 shed on the nature of the sun itself, and the laws which govern that 

 flow of light and heat through which alone we ourselves live and move. 

 Experience seems to indicate that, according as these wonderful phe- 

 nomena are studied with or without the spectroscope, they are assimi- 

 lated more, in the observer's mind, with such terrestrial motions as 

 those we call eruptions in the first instance, or cyclones in the second. 

 It would be generalizing from a partial view, therefore, to present the 

 reader with any single hypothesis at present, especially while those 

 versed in the study find so much that, on any hypothesis, is still mys- 

 terious. 



FERMENTS, FERME^N^TATIONS, AND LIFE. 



Br FERNAND PAPILLON. 

 TRANSLATED BY A. R. MACDONOUGH. 



UNTIL very lately, all fermentations were supposed to be pro- 

 duced by the spontaneous decomposition of organic matter with- 

 in a fermentable liquid. It was said that on contact with air this 

 organic matter undergoes a special change which gives it the character 

 of leaven, and this was regarded as an agent having the power of 

 spreading decomposing movement. It is true, brewer's yeast had 

 long been well known ; the facts of its cellular composition and its 

 organization were familiar ; but no relation was recognized between 

 this organized condition and those phenomena of fermentation pro- 

 duced by yeast in saccharine liquids, such as grape-juice or the wort of 



