THE VICTORIAN NATURALIST. 17 



ON "RED RAIN," WITH SPECIAL REFERENCE TO 

 ITS OCCURRENCE IN VICTORIA. WITH A NOTE 

 ON MELBOURNE DUST. 



By F. Chapman, F.R.M.S., and H. J. Grayson. 



{Read he fore the Field Naturalists' Cluh of Victoria, llth Mai/, 1903.) 



Jntroductort/ Remarks. — Natural phenomena, meteoric or other- 

 wise, which happened to be beyond the common order of things 

 were regarded by our forefathers with mingled feelings of awe 

 and superstition. Many of the mysterious phantasies of the past 

 have been dissipated by the growth of accurate knowledge, and 

 not least among these is the phenomenon, common enough in 

 certain districts, and under peculiar conditions, of the so-called 

 blood-rains. This appearance, which was regarded by the 

 credulous and unscientific mind in a more or less literal sense, 

 and presaging calamity in one form or another, is to us merely a 

 dust-laden shower, brought about by the rain falling during a 

 dust storm. 



Although showers of red rain, when particularly dark in colour, 

 are referred to as blood-rain, it is rare to find the colouring 

 material so vivid as to cause the name to be merited, mud -rain 

 being often more appropriate. 



Other similar appearances, produced in a different way, and by 

 the agency of Protophytes, are variously known as " gory dew " 

 {Pahnella cruenta), found on damp walls, and resembling in 

 colour coagulated blood ; and the " red snow " found in the 

 arctic and alpine regions colouring extensive tracts of country, 

 which is either a species of Palmella or possibly a Protococcus. 

 These latter appearances, however, are distinctly due to organic 

 growth, and have nothing in common with red rain. 



The "yellow rain," or "sulphur showers," which, by the way, 

 are not due to sulphur, are frequent in some countries, and not 

 confined to any in particular. They are caused by an exceptional 

 quantity of pollen, chiefly coniferous, being included in the 

 condensing moisture and brought down with the rain. 



The physiographical conditions required for the production of 

 mud-rains are, obviously, a desert tract of country, where fine 

 impalpable dust may be caught up by the wind, and the 

 inclusion of this dust in a moisture-laden stratum of air. The 

 result is a shower of muddy rain, which often takes place at 

 distances far removed from the source of the dust. It is possible 

 that the process of condensation may be hastened by the 

 presence of dust particles, as seems to be the case during 

 volcanic outbursts. 



In many regions dust storms are so generally prevalent as to 

 result in the deposition of layers of fine sediment, which mantle 



