Prof. Agardh's Memoir on the Red Snow, $c. 171 



red to green. Nor is the colour determined wholly by light; it is aided 

 by the nature of the body on which it strikes, but in a manner quite un- 

 intelligible to us. 



M. Agardh then goes on to argue, that as white bodies, very dissimilar 

 in appearance and nature, produce the same effect in the formation of red 

 colouring matter, so we must not be surprised to find, that a plant, such 

 as Uredo nivalis, which is found on the highest Alps in the most northern 

 latitudes, in the cold of winter, and only on the surface of the snow, is 

 again found in the plains, in summer, and on glittering limestone.* 

 Hence it must be inferred, that the existence of the Alga of the red snow 

 must be accounted for by the gradual melting of the snow from the in- 

 tensity of light ; and not, as some suppose, that it is washed down from 

 the neighbouring rocks, or, as might be inferred from the information 

 given from Italy, that it has fallen from the atmosphere. In regard to 

 the first supposition, were such the case, De Saussure and the English 

 navigators would have noticed such a red stream running down the sides of 

 the mountains, a fact which Saussure denies, and upon which the English 

 are silent. 



As to the accounts given by so many men of science, that the Red Snow 

 falls from the air, I need only refer to one circumstance, namely, that all 

 the accounts agree in asserting, that this Red Snow fell in the night, 

 which is as much as to say, that no one has seen it fall. Why, we may 

 ask, should the snow only fall red in the night, when no one can discern 

 it to be red, and not in the light of day, before which white can become 

 red? 



I am, on the other hand, of opinion, that the Lepraria kermesina is 

 called into existence by the vivifying power of the sun's light, after its 

 warmth has caused the surface of the snow to dissolve, combined with 

 that incomprehensible property in white snow, of producing a colour ; ne- 

 vertheless, that it first attracts the eye when there is a some considerable 

 quantity, in the same way as we do not see the colour of the drops of wa- 

 ter till they have accumulated in the ocean. This opinion is not only con- 

 firmed by De Saussure's observation, who expressly says, " qu'on ne 

 trouve la neige rouge que dans une certaine periode de la fonte des 

 neiges, car lorsqu'il ne s'en est pas beaucoup fondu, la quantite du residu 

 rouge est tres petite, et s'il en est trop fondu, on n'en trouve rien;" but 

 also by the recollection, that the time that this coloured snow appeared in 

 Italy, namely in March and April, is the time when the snow begins to 

 melt. 



An assertion of Captain Ross's does, indeed, appear to come in opposi- 

 tion to this, namely, that the Red Snow extends very far below the sur- 

 face, in some places reaching to the ground at a depth of twelve feet ; but 

 then, this is directly contradicted by another traveller of the same expedi- 



• This at least we guess to be the meaning of the author, but the theory itself 

 teems to us to be very abstruse ; and probably from too imperfect an acquaintance 

 with the German language, we may not entirely have given the passage correctly. 

 — H. 



