378 PHILOSOPHICAL TRANSACTIONS. [aNNO \73Q. 



room, that what was under this surface might slide off, or perhaps because the 

 parts under this surface had been hollowed a long while before, by the waters 

 which passed between this surface and the stratum of fat clay. Other parts, 

 which were much more in number, rolled all together towards the valley, and 

 whole pieces of vineyards are still seen, with the props remaining upright. 

 There are again other parts, which in tumbling were overturned in ditferent 

 manners. 



This accident is not without example in the province of Auvergne : there has 

 not indeed been so considerable a one before, yet it has often happened, that 

 pieces of earth, of a quarter or half an acre, have separated all in one piece, 

 from the top of a hill, and slid down visibly on the lands below. 



On the Worms* which destroy the Piles on the Coasts of Holland and Zealand. 

 By Job Baster,f M. D. F. R. S. N° 435, p. -276. 



In the year 1730, the persons appointed to take care of the dykes on our 

 coasts, observed that the piles made of the hardest oak, defending the coasts of 

 the Netherlands against the sea, were eaten through in a few months, so as to 

 be broken by the least external force. Surprised at this uncommon and danger- 

 ous phenomenon, they inquired into its cause, and saw that a kind of worms, 

 before that time very scarce, but now increased to an incredible number, had 

 in so short a time eaten into those piles, between the highest and lowest water- 

 marks, and threatened very great damage to the inhabitants of these countries. 



If a pile of the hardest oak has stood 6 months on the shore, and be taken 

 out in summer or autumn, there appears mud and filth sticking to its outer 

 surface ; which being scraped off with a knife, discovers a vast number of holes, 

 hardly so large as pins heads. 



Viewing this mud through a microscope, there are seen, 1. A number of 

 whitish points, not larger than grains of sand. — 2. Some very small worms. 



The whitish points seem to be the eggs of this insect, and the worms to be 

 such as are already hatched from them ; and these worms gradually perforating 



* The animal here described is the teredo navalis of Linnaeus. 



t Job Basterj an ingenious Dutch physician and naturalist, distinguished himself by a controversy 

 with the celebrated Mr. Ellis, relative to the animal nature of the corallines, which Dr. Baster con- 

 sidered as rather the habitations of the inclosed polypes than as forming a constituent part of the ani- 

 mal. His chief work however is his Opuscula Subseciva, containing observations on various marine 

 animals. These interesting observations were continued, in distinct parts, from the year 1759 to 

 1765, and are illustrated by very instructive plates. They relate to the propagation and ovaria of 

 shell-fish in general; the ostrea, mytuli, pholades, and tellinae; and the structure of several specie* 

 of the testacea is explained in a satisfactory manner. 



