FLOATING ISLANDS 3°3 



FLOATING ISLANDS 



BY SIDNEY POWERS, B.A. 



WILLIAMS COLLEGE 



IF one should see in a story the statement that a floating island 100 

 feet square, upon which were growing trees thirty feet in height, 

 was used hy the hero as a place of refuge, and that the island traveled 

 1,000 miles out to sea, he would probably accuse the author of an abuse 

 of the imagination. But such an island — without the hero — was seen 

 off the coast of North America and is known to have traveled at least 

 1,000 miles. Floating islands also occasionally occur in the lakes of 

 some of our northern states. It is the purpose of this article to point 

 out the location of some of these islands and to explain their origin. 



In order to understand the formation of a floating island let us 

 imagine a pond on the edges of which rushes and grasses are growing. 

 These gradually push their way out into the deeper water, leaving a 

 mass of decaying vegetable matter upon which, in time, mosses such as 

 sphagnum may secure a foothold, and start a shelf which will extend 

 out into the water. As soon as the sphagnum has become well estab- 

 lished, water-loving plants and shrubs such as alders, sheep laurel and 

 sweet gale will grow with the moss. Cranberries and pitcher plants 

 may also aid in the formation of the mat, forming the familiar cran- 

 berry bog. This shelf will be attached to the shore for several feet, the 

 distance depending on the depth of the water, but the peat will seldom 

 attain a thickness of more than three feet. After the mat has become 

 firm, black spruces and larches may grow upon it, often anchoring it 

 and always making it more compact by means of their roots. Such a 

 mat is illustrated by the drawing on page 304. 



After the shelf has extended itself some distance into the pond, if 

 the water level is raised unusually high by excessive rainfall or the con- 

 struction of a dam across the outlet, the mat may break off and form a 

 floating island. This island will either become attached near its former 

 position by roots extending underneath it, or it will float around the 

 lake. 



In case the pond is small and nearly circular the mat may surround 

 it. If the water in the pond is raised, at the time when all but the 

 center of the pond is overgrown, an atoll or ring-shaped island may be 

 formed. For the persistence of this atoll the water must remain at its 

 high level and the atoll must become anchored. 



Finally, let us suppose that the vegetation completely covered the 

 lake before the water rose. There is sufficient elasticity in such a mat 

 to permit it to rise slightly with a rise in the water level. The mat, 

 however, is not sufficiently elastic to permit its center to rise more than 



