210 NATURAL HISTORY. [cH. XIV. 



spectacle which is scarcely to be conceived, much 

 less expressed. The snow, when it falls most 

 thickly and in the largest flakes, could not fill the 

 air more than it was filled by these ephemerae." The 

 steps on which Reaumur stood were covered by 

 layers of these insects, measuring in no place less 

 than two or three inches in depth ; in most, more 

 than four. The surface of the water was covered 

 for a space of six feet square by a mass of these in- 

 sects, and as the current slowly bore them onward, 

 the space was speedily filled by an equally plentiful 

 supply. This living rain more than once obliged 

 him to quit his station, for his mouth, nostrils, and 

 eyes were filled by the incessant showers of these 

 insects, which, striking his face, incommoded him 

 much. They who held torches were surrounded by 

 swarms of these insects, which, arranging them- 

 selves in innumerable circles around the flame, at- 

 tracted the attention of the most incurious. Wheth- 

 er this was an optical delusion, as Kirby shrewdly 

 conjectures, or whether they really were zones of 

 living beings flitting round the pure element, is not 

 quite clear. But the individuals which composed 

 these circles ranged only for a very few seconds 

 round the torch, and then fell on the ground, or per- 

 ished on the earth. 



It is thus that these creatures burst forth from 

 the waters : it would appear, however, that though 

 the time of the year in which they become aerial 

 beings differs in different countries, yet the insects 

 of the same country appear at the very same time 

 each year ; nay, further, the very hour of the day at 

 which they should rise from the water into the air 

 is fixed to such a nicety, that on each succeeding 

 day these swarms of insects come forth at the pre- 

 cise instant at which they had appeared the prece- 

 ding day. " Whatever," says Reaumur, " may have 

 been the temperature, whether the day has been 

 sunny or rainy, the hour at which our ephemerae be- 



