SCIENCE OF AGRICULTURE. Ill 



fore. The melting of metals and the conversion of 

 liquids into steam are familiar illustrations of this 

 theor}'. In the temperature of our atmosphere, dif- 

 ferent bodies exist naturally in the three forms. But 

 the solid particles which surrounded by caloric com- 

 pose, for example, the atmospheric air, may be indi- 

 vidually as heavy as the particles of lead, and capable 

 of uniting with the particles of lead, and by this union 

 produce a substance very unlike either air or metalic 

 lead — the well-known pigment red lead. 



By such changes and combinations of the particles 

 of matter, although only forty nine different kinds of 

 matter are known, all the endless varieties of substan- 

 ces which exist around us are formed, and the parti- 

 cles of gases or fluids as readily unite with solids as 

 the particles of solids with each other. Hence, in 

 speaking of the constituents of soils, manures, and 

 vegetables, we shall have frequently to describe such 

 combinations. Component parts of fluids and gases 

 become solids, and component parts of solids again 

 become fluids and gases, both in the formation and 

 decay, or decomposition of vegetables. These pre- 

 liminary explanations, if carefully studied, will, it is 

 hoped, be sufficient to enable those who have read 

 nothing on Chemistry, to understand what we are 

 about to say on the subject of soils, manures, and 

 vegetables. 



Soils. 



All geologists and chemists agree in considering 

 soils the result of the pulverized and decomposed 

 portions of rocks, with the addition of salts and veg- 

 etable and animal substances. Nearly all the rocks 

 which exist in large quantities, are composed chiefly 

 of silica or flint, alumina, pure clay, lime and iron. 

 Magnesia exists in small quantities in many rocks 

 and in the serpentine and soapstone in large portions. 

 Manganese, another metal, in small quantities in the 

 rocks, and consequently in the soils of New England. 

 Potash and soda exist also in most of our rocks. 



