LECTURE XII. 
211 
that can be imagined as to shape^ but still preserv- 
ing its particularity of surface. 
Some of the Madrepores bear an appearance 
60 perfectly similar to that of some kind of Mush- 
room, that they have often been considered as pe- 
trified Mushrooms. Tlie Madrepores in general 
as well as the other larger Corals, are chiefly found 
about tlie coasts of the Indian islands, where they 
are so numerous as to form vast rocks, their animals 
seeming to carry on their work by a kind of instinct, 
continuing to grow in such a manner as to encircle 
a vast body of water, so as to form a calm or smooth 
bay. Within the tropical seas, according to the 
learned Dr. Reinhold Forster, in his ingenious dis- 
sertation on India, there are numerous small 
islands, but little elevated above the surface of the 
sea. All these are the work of marine Zoophyte 
Vermes, which raise on all sides their calcarious 
matter, from which at length are formed rocks 
and stony shallows, very dangerous to navigators. 
Easterly winds being most prevalent in these seas, 
the animals, as if actuated by instinct, endeavour 
to exclude the waves driven by the winds, by 
means of their stupendous works; and therefore, 
carrying on their habitations, they extend them 
