170 SELECTIONS FROM ADDRESSES. 



composition and specific action of most substances called ma- 

 nures. They may be divided into two classes : the first, em- 

 bracing the various salts useful upon land ; and the other, con- 

 sisting of vegetable or animal matter mixed with salts. The 

 salts are such as common salt, nitre, phosphate of lime, or bone 

 ashes, limestone, marl, nitrate of lime, potash, soda, &c. &c. 

 These, in their pure state, do not afford much nutriment to 

 plants ; but they act upon the nutriment, and prepare it for the 

 organs of the plant, by rendering it soluble and decomposing it. 

 The common manures, or a large part of them, are converted, 

 when mixed with the soil, into what is called geine, or humus. 

 But this is not in a proper state to be taken up by the roots, 

 until acted upon by other substances, when it becomes soluble, 

 or produces carbonic acid. Common manures usually contain 

 more or less of the salts ; but, being most of them soluble, they 

 are carried away by rains ; and hence the value of new supplies. 

 Nor does it usually require but a small quantity, as the example 

 of ashes, and gypsum, and phosphate of lime evinces. The 

 latter, in the state of bone dust, where the phosphate is mixed 

 with carbonate of lime and cartilage, is a manure so concen- 

 trated, that one ton of it is equal to 14 tons of farm yard ma- 

 nure ; and almost equally concentrated is guano, and some 

 other compounds now used upon land. 



But there is not time to go into specific details as to the chem- 

 ical action of manure. Here, however, chemistry has done a 

 noble work for agriculture ; and yet the field is not all explored. 



Chemistry has also done, and is destined to do a great work, 

 in this same field, by pointing out new manures. It is well 

 known that some of the most valuable now in use have been 

 suggested, or first prepared in a proper manner, by this science. 

 It teaches us that whatever substance contains such salts and 

 humus as will produce ammonia, will answer for manure ; and 

 that the value of the manure depends upon the quantity of am- 

 monia produced. And among the substances to which the 

 farmers of Massachusetts will do well to give more attention 

 than they have done, aided by the valuable suggestions of 

 Dr. Dana, in his Muck Manual, is the black mud and peat of 

 our swamps. From this single source I doubt not, with the aid 



