64 THE MICEOSCOPE. 



rerice of no fewer than 340 showers of blood-rain 

 and dust-rain. In this treatise he advances the 

 remarkable position, " that there must exist some 

 law of nature according to which these living 

 organisms may develop themselves in the air." 

 He also calls special attention to extraordinary 

 cases, viz., the dust-shower at Lyons in 1846, 

 where an immense mass of matter must have 

 fallen, weighing 7200 cwt. ; the occurrence of red 

 mist, and then a descent of blood-rain at Locarno, 

 near Lago Maggiore in 1755, leaving a red de- 

 posit, which must have covered forty German 

 miles square ; and a shower of dust which fell 

 upon the deck of a vessel in the Atlantic ocean, 

 about 500 miles from the west coast of Africa. 

 In this last case, the animalcules, fifteen species 

 in all, which fell with the dust, when collected 

 and examined by Darwin, proved that the wind 

 must have floated the mass from the shores of 

 South America. 1 This fact goes to support a 

 remarkable theory stated by Humboldt in his 

 Aspects, namely, that " many of these agglo- 

 merations of silicious-shelled microscopic organ- 



1 It is to be remembered, that not a few of the Infusoria 

 are "to be found only in certain geographical areas. 



