14 Introduction 



primeval instincts remain. And where the waters are 

 clean, and shores unspoiled, thither we still go for rest, 

 and refreshment. Where fishes leap and sweet water 

 lilies glisten, where bull frogs boom and swarms of 

 May-flies hover, there we find a life so different from 

 that of our usual surroundings that its contemplation 

 is full of interest. The school boy lies on the brink of a 

 pool, watching the caddis worms haul their lumbering 

 cases about on the bottom, and the planctologist plies 

 his nets, recording each season the wax and wane of 

 generations of aquatic organisms, and both are satisfied 

 observers. 



The study of water life, which is today the special 

 province of the science of limnology*, had its beginning 

 in the remote unchronicled past. Limnology is a 

 modern name; but many limnological phenomena were 

 known of old. The congregating of fishes upon their 

 spawning beds, the emergence of swarms of A lay-flies 

 from the rivers, the cloudlike flight of midges over the 

 marshes, and even the "water bloom" spreading as a 

 filmy mantle of green over the still surface of the lake — 

 such things could not escape the notice of the most 

 casual observer. Two of the plagues of Egypt were 

 limnological phenomena; the plague of frogs, and the 

 plague of the rivers that were turned to blood. 



Such phenomena have always excited great wonder- 

 ment. And, being little understood, they have given 

 rise to most remarkable superstitions. f Little real 



*Limnos = shore, waterside, and logos = a. treatise: hydrobiology. 



f The folk lore of all races abounds in strange interpretations of the simplest 

 limnological phenomena; bloody water, magic shrouds (stranded "blanket- 

 algae"), spirits dancing in waterfalls, the "will o' the wisp" (spontaneous com - 

 1 mstion of marsh gas), etc. Dr. Thistleton Dyer has summarized the folk lore 

 concerning the last mentioned in Pop. Sci. Monthly 19:67, 1S81. In Keightly's 

 Fairy Mythology, p. 491 will be found a reference to the water and wood maids 

 called Rusalki. "They are of a beautiful form with long green hair: They 

 swing and balance themselves on the branches of trees, bathe in lakes and 

 rivers, play on the surface of the. water, and wring their locks on the green 

 mead at the water's edge." On fairies and carp rings see Theodore Gill in 

 Smithsonian Miscellaneous Collections 48:203, 1905. 



