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find but one species of Diatoms and one of Desmids thus de- 
posited. Nor would he have supposed that a species of a 
distinctly marine genus of Diatoms (Triceratium), for Smith’s 
Triceratium exignum found in fresh water, does not belong to 
this genus, but to the just as well marked fresh water genus 
Tabellaria, would come from the waters of a lake. However, 
Mr. Ernst’s description of the substance deposited as yellow 
and clayish, will, I think, lead us to define what it really was. 
But before saying what I wish to on this subject, I would 
call attention to another letter, published in the same period- 
ical, on this subject. On page 160 of Vol. IV. another gentle- 
man quotes authorities, tending as he thinks, to confirm such 
showers of solid particles, or, at least, their appearance after 
rain, and upon the ground or vegetation, and thereby falls 
into some errors fully as great as those of Mr. Ernst, Thus, 
after quoting a passage in Pliny, where arain of “iron” 
along with “sponges,” is spoken of, he goes on to explain 
that the iron and sponges here mentioned are one and the 
same thing, namely the now well-known “red snow.” And 
it is a curious fact that in the books of authors who ought 
to know better, we find it stated that there have been cases 
in which a red-colored matter has descended from the air, upon 
the ground and vegetation, and that on examination by means 
of the microscope it has been ascertained to be made up of in- 
dividuals of a minute perfect plant, which has been taken up 
by the wind or otherwise, from its natural habitat, which is in 
or upon the surface of water, and thereafter rained down upon 
the earth. Furthermore we find a record as to the occurrence 
of the so-called “red snow ” in Washington Territory, by Mr. 
George Gibbs, in the American Naturalist, Vol. V. page 116, 
which presents us with some further information on this point, 
and will serve as an introduction to what I have to say on 
this subject. 
Mr. Gibbs states that in the summer of 1858, at an altitude 
of 6500 feet on the Cascade Mountains, he found the “red 
snow.” He disgusted the man who first brought it to him, 
by eating it, and examination by means of a lens showed it 
to consist of “ tadpole shaped bodies, with rounded head and 
