Microscopic Forms in Dust-showers and Blood-rain. 27 



Polygastrica, 57 ; Phytolitharia, 46 ; Polythalmia, 8. 



Besides these, there are seven kinds of particles from 

 plants, and are fragments from an insect. Seventeen of the 

 species are marine, and the other 102 of fresh-water origin. 

 There is no evidence of volcanic origin. 



VI. Second specimen from the Genoa shower of the \^th 

 of May 1846. — All but one of the forms mentioned were 

 observed in the former specimen of the dust. 



VII. Storm of red snow in Puster Valley, in Tyrol, March 

 31, 1847. — This red snow owed its colour to a coloured dust, 

 much resembling that of the Atlantic. Its tint is brownish 

 red. 



It afforded, as obtained at two localities, 66 organic forms, 

 22 of which were Polygastrica, 28 Phytolitharia, 2 Polytha- 

 lamia, 13 particles of plants, and 1 of an insect. The large 

 majority of the species are known fresh water and conti- 

 nental forms ; only 4 to 6 species are unknown, 2 are ma- 

 rine, namely, Coscinodiscus radiolatus, and a Spiroloculina (?). 

 There is a remarkable resemblance in the colour and cha- 

 racter of the dust to that of the Atlantic, Genoa, and Lyons, 

 and an identity in many of the species ; 46 species out of the 

 QQ occur in the Sirocco and Atlantic dust ; 12 Polygastric 

 species, and 20 Phytolitharia are common to the Atlantic 

 showers and the Tyrolese snows. This uniformity of cha- 

 racter over regions so widely separate, yet in nearly a com- 

 mon latitude or zone, and in so many distinct examples 

 through a number of years is most surprising. 



VIII. Dust ivhich fell in Italy in 1803, and in Calabria in 

 1813. — The former of these showers is represented as coming 

 from the south-east. It afforded 49 species, and that of 

 Calabria 64. Out of the 49, 39 have been observed in the 

 more recent showers ; and out of the 64, 51 are like the more 

 recent. These showers, although ten years apart, have 28 

 species in common, or about one-fourth. In both nearly all 

 the species are of fresh water or continental origin. In both, 

 as in other showers, the most abundant species are Eunotia 

 amphioxys, Gallionella granulata, G, crenuta, G. distans, G. 

 procera, Lithodontia, Lithostylidia. In both, also, there are 

 four South American forms; Coscinodiscus flavicans from Peru 

 and St Domingo ; Navicula undosa from Surinam ; Stauroneis 



