38 Economical Geology. 



Substitute for Fuller's Earth. 



The common clay in the Connecticut valley, has recently been 

 employed in Northampton, in the place of fuller's earth, in cleansing 

 cloth. A considerable quantity of it has also been sent down the 

 river, for use in other places. This clay is fine grained, and when 

 dry, adheres strongly to the tongue. It is said to answer exceed- 

 ingly well in the place of fuller's earth ; on this point however, I have 

 my information at second hand. A clay of precisely the same char- 

 acter has recently been put into my hands from Leominster, where it 

 occurs in alternating layers with, sand. Some of the sand of this 

 tertiary formation, especially in the gneiss region, is of a delicate 

 white color, and quite pure. In some cases, when its finest particles 

 are mixed with clay, it will answer very well for giving a polish to 

 brass and other metals. This variety is found abundantly in Shutes- 

 bury. 



Clay used in the Manufacture of Alum. 



The white clay of Martha's Vineyard, is employed extensively in 

 the manufacture of alum, in Salem ; by the process of Chaptal, I sup- 

 pose ; although the details are, I believe, kept secret. By his method, 

 sulphur and nitre are burnt in a chamber with the clay, 'which, after 

 a considerable time, is lixiviated, and the ley evaporated. There is 

 indeed, a variety of Clay which contains sulphur, that will produce 

 alum without the addition of other materials ; but I cannot believe 

 that from the Vineyard to be of this description. At any rate the 

 alum which the Salem company produce, is of a good quality, and is 

 made in large quantities. They formerly obtained their clay from 

 Gay Head ; but they now procure it of a better quality from the west 

 side of the island, in Chilmark, 



Clay as a Manure. 



Writers on agriculture, speak of clay as next in value to marl, for 

 manuring light and sandy lands ; and I cannot but think that our far- 

 mers have yet something to learn on this subject. Marl, they cannot 

 procure, but at a great expense ; but clay is usually at hand and we 

 have very much of the land which it will help. Yet I am not aware 

 *hat in any instance the experiment has been thoroughly made. 



Marl. 

 Marl for our farmers, scarcely exists in the State, except in a few 



