MINUTE ORGANISMS. 143 
troops of artisans that we cannot see. Upon coasts occupied by 
the corallines, the reef-building animalcule does not work near 
the mouth of rivers. Hence the change of the outlet of a stream, 
often a very easy matter, may promote the construction of a 
barrier to coast navigation at one point, and check the forma- 
tion of a reef at another, by diverting a current of fresh water 
from the former and pouring it into the sea at the latter. Cases 
may probably be found, in tropical seas, where rivers have pre- 
vented the working of the coral animalcules in straits separating 
islands from each other or from the mainland. The diversion 
of such streams might remove this obstacle, and reefs conse- 
quently be formed which should convert an archipelago into a 
single large island, and finally joi that to the neighboring con- 
tinent. 
Quatrefages proposed to destroy the teredo in harbors by im- 
pregnating the water with a mineral solution fatal to them. 
Perhaps the labors of the coralline animals might be arrested 
over a considerable extent of sea-coast by similar means. The 
reef-builders are leisurely architects, but the precious coral 
is formed so rapidly that the beds may be refished advantage- 
ously as often as once in ten years.* It does not seem impossi- 
ble that branches of this coral might be attached to the keel of 
a ship and transplanted to the American coast, where the Gulf 
stream would furnish a suitable temperature beyond the clima- 
tic limits that otherwise confine its growth; and thus a new 
source of profit might perhaps be added to the scanty returns 
of the hardy fisherman. 
In certain geological formations, the diatomacese deposit, at 
the bottom of fresh-water ponds, beds of silicious shields, valu- 
able asa material for a species of very light firebrick, in the 
manufacture of water-glass and of hydraulic cement, and ulti- 
* The smallest twig of the precious coral thrown back into the sea attaches 
{tself to the bottom or a rock, and grows as well as on its native stem. 
See an interesting report on the coral fishery, by Sant’ Agabio, Italian Con- 
sul-General at Algiers, in the Bollettino Consolare, published by the Depart- 
ment of Foreign Affairs, 1862, pp. 139, 151, and in the Annali di Agricoliura 
Industria e Commercio, No. ii., pp. 360, 373. 
