830 OYSTERS, AND ALL ABOUT THEM. 



No account has been taken of the number of mature 

 or young oysters removed by the tongers, and the estimates 

 are based upon observations made at the commencement 

 of the fishing season, when, the prices being low, a smaller 

 number of dredgers would be at work ; therefore, there is 

 every reason to believe that the estimate of both classes of 

 oysters is under rather than above the real number removed. 

 We have then, aside from the ravages of the drills, a yearly 

 destruction of over 64,000,000 young, and the removal of 

 184,000,000 mature oysters, to account for the deterioration 

 of the beds. 



SPECIFIC GRAVITIES. 



Before I begin this part of Lieutenant Winslow's valu- 

 able work, I must, in behalf of my non-scientific patrons, 

 respectfully solicit the scientific reader's indulgence for 

 presuming to give a definition of the above title. 



According to the Dictionary, specific gravity means 

 "the weight of a body compared with another of equal 

 bulk, taken as a standard," but the definition that will suit 

 my purpose better, and, at the same time, instruct the 

 reader in a more desirable and comprehensive manner, is 

 that given by Captain Maury in his very valuable work on 

 the Sea (h), wherein he shows that the general circulation 

 of the sea is dependent upon its specific gravity, and the 

 constant and successful efforts of that element to preserve 

 an uniform condition, and he illustrates the idea in the 

 following ingenious manner :- 



" Let us suppose a globe of the earth's size, and with a 

 solid nucleus, to be covered all over with water two hun- 



(h] The Physical Geography and Meteorology of the Sea. By 

 Captain Maury, LL.D., Superintendent of the National Observatory, 

 Washington. Sampson Low, Son, & Co., London, 1861. Ninth 

 edition. 



