194 ON THE COMPOSITION OF SOILS, &C. 



the quantity of water supplied ; and the expo- 

 sure to the sun, air, and light, determine the 

 natural produce of the general substance or soiL 



From what is here said, so far from earth 

 worms being an enemy to the farmer, they are 

 his best friends ; without them his lands would 

 soon become impenetrable to air or water, and 

 hence sterile and unproductive ; and it is cer- 

 tain earth worms never wound, or prey upon 

 the sound or living parts of seeds, roots, or 

 plants. 



As Mr. Kirwan observes, the calcareous earths 

 seem to be the most necessary as a component 

 part of the food of plants ; from its peculiar 

 chemical powers, it is also most necessary as an 

 operative agent in the preparation and reduction 

 of animal and vegetable substances, and in due 

 proportion, it is also well adapted to render the 

 other more tenacious substances permeable to 

 water and air, all which have been before ex- 

 plained. 



But that state, in which the operation of the 

 calcareous earths have been found to be the 

 most powerful, is lime. This singular substance 

 is never found in a native state ; but from the 

 simplicity of its formation, and very extraor- 

 dinary powers, its uses and application in the 

 arts is most extensive, and perhaps no produc- 

 tion, from its universal adaptation, ever obtained 



