362 INVERTEBRATA OF MASSACHUSETTS. 



The manufacture of shell lime is carried on extensively by Mr. 

 Kingsley, of Boston. The shells are collected from the various 

 oyster shops, and are given to him for the trouble of removal. Twenty 

 to thirty thousand bushels are thus collected and burned annually. 

 The lime is sold at twelve and a half cents per bushel. 



Shell lime is also extensively employed in masonry ; and it is with- 

 in the memory of man when no other lime was known for building, 

 along the seaboard. 



By the addition of the proper materials, clay and magnesia, Mr. 

 Kingsley prepares an excellent hydraulic cement, which is used not 

 only for laying drains, cisterns, &c., but its whiteness renders it suita- 

 ble for the manufacture of fountains, vases, and ornamental articles, 

 which are to be placed in exposed situations. 



We find nothing else which is employed in the arts, except the 

 SCOLLOP SHELL, (Pecten concentricus,) which is so extensively used 

 in the manufacture of card-racks, pin-cushions, &c. 



The animals of several shells (Purpura and Buccinum) afford a 

 juice, when they are bruised, which dyes a brilliant purple. The 

 ancients are supposed to have derived all their purple dye from this 

 source ; but other more available articles have entirely superseded its 

 use. 



PEARLS of various colors and considerable size and beauty are often 

 found in both salt and fresh water mussels. They were once highly 

 valued in England, but are not sought for at the present day. 



This summary, short as it is, and containing little that is not already 

 familiar, presents, nevertheless, all that is known to be of direct use 

 and benefit to man. Some may hence be disposed to inquire, " Of 

 what use, then, is the study of so many others which are apparently 

 useless ? " A few words only need be said to such objectors. In the 

 first place, all of God's works are wonderful, and worthy of study. 

 Again, negative knowledge is useful. The most useful sciences are 

 made up of trivial facts. Newton's apple, Young's soap-bubble, and 

 Galvani's frog, have given hints which have led to almost the complete 

 developement of some of the most important natural laws which affect 

 us. And again, so limited is our knowledge of the designs of the 

 Author of nature, that animals which appear of little importance in 

 relation to ourselves, are perhaps as necessary to the general plan of 

 the Creator, as those which we place at the top of the scale of being. 



