150 G. C. KAROP ON RED RAIN DUST FROM AUSTRALIA. 



any case both it and its included remains are almost ubiquitous ; 

 the diatoms, etc., may have been rolled about for centuries or 

 aeons. Eeduced to impalpable powder by sun, rain, and wind, 

 it has, perhaps, been borne aloft by some violent storm and 

 travelled round the world ; or, on the other hand, it may 

 have been deposited by the first shower not very far from its 

 birthplace. 



The phenomenon, while hardly common, is yet not of very in- 

 frequent occurrence. This very year it has appeared in Southern 

 Italy and other places, and, of course, given rise to numerous 

 communications to the newspapers. The first really scientific 

 exposition of the causes of this startling phenomenon, known to 

 me at least, was Prof. C. G. Ehrenberg's work entitled '' Passat 

 Staub und Blut-Pegen. Ein grosses organisches unsichtbares 

 Wii'ken und Leben in der Atmosphaere. Mit 6 colorirten 

 Kupfertafeln," published in the Ahh. Berliner Akad., Berlin, 

 1849, and other communications on the subject submitted to 

 and published by the same Academy in 1862, and later. 



The two most common origins of so-called Blood-rain are, firstly 

 as above — viz., extremely finely comminuted particles of red earth 

 with various inclusions, raised by some tornado and carried, 

 it may be, for immense distances from its place of birth ; and, 

 secondly, to the sometimes extraordinary development in a veiy 

 short space of time of the lowly protophyte known as Spherella 

 {Protococcus) pluvicdis, which, besides its usual green, in certain 

 peculiar and not very well ascertained conditions sometimes 

 assumes a red colour, and was in this state formerly differentiated 

 as Haernatococcus. Either this and allied forms such as, for 

 instance, the hardly separate one known as S. nivalis, causing 

 " Red-snow," or Bacillus prodigiosus, or other chromogenous 

 bacteria, and some of the Fahnellaceae, as F. cmienta, occasionally 

 appear with extreme suddenness, and among the unlearned give 

 rise to no little alarm, and to dire prognostications of war, famine, 

 and sudden death. 



Joarn. Quekett Microscopical Club, So: 2, Vol. VJII. 2io. 40, November 1901. 



