MINUTE ORGANISMS. 
123 
ations are not less destructive to fish which live or spawn in 
fresh water. Mill dams impede their migrations, if they do 
not absolutely prevent them, the sawdust from lumber mills 
clogs their gills, and the thousand deleterious mineral sub¬ 
stances, discharged into rivers from metallurgical, chemical, 
and manufacturing establishments, poison them by shoals. 
Minute Organisms. 
Besides the larger creatures of the land and of the sea, the 
quadrupeds, the reptiles, the birds, the amphibia, the Crus¬ 
tacea, the fish, the insects, and the worms, there are other 
countless forms of vital being. Earth, water, the ducts and 
fluids of vegetable and of animal life, the very air we breathe, 
are peopled by minute organisms which perform most import¬ 
ant functions in both the living and the inanimate kingdoms 
of nature. Of the offices assigned to these creatures, the most 
familiar to common observation is the extraction of lime, and 
more rarely, of silex, from the waters inhabited by them, and 
the deposit of these minerals in a solid form, either as the 
material of their habitations or as the exuviae of their bodies. 
The microscope and other means of scientific observation 
assure us that the chalk beds of England and of France, the 
coral reefs of marine waters in w T arm climates, vast calcareous 
and silicious deposits in the sea and in many fresh-water 
ponds, the common polishing earths and slates, and many 
species of apparently dense and solid rock, are the work of the 
humble organisms of which I speak, often, indeed, of animal- 
culse so small as to become visible only by the aid of lenses 
magnifying a hundred times the linear measures. It is pop- 
dation was produced in the Indalself, which rises in the Storsjo in Jemtland, 
by drawing off into it the waters of another lake near Ragunda. The flood 
destroyed houses and fields; much earth was swept into the channel, and 
the water made turbid and muddy; the salmon and the smaller fish for¬ 
sook the river altogether, and never returned. The banks of the river 
have never regained their former solidity, and portions of their soil are 
still continually falling into the water .—Bern genom Sverge , ii, p. 51. 
