On Lime and Marls, 207 



dred to three hundred loads are put on. But if the 

 most pure calcareous substances are the most valua- 

 ble manures, how much more pure must gypsum be, 

 of which one or two bushels to an acre produces such 

 an effect ? And how much purer must we suppose the 

 limes, which require no more than from twenty five to 

 fifty or sixty bushels to an acre ? But the contrary has 

 been shown to be the fact. It is also a fact, that those 

 limes, of which a great quantity is required for ma- 

 nure, when used in building admit of a very small 

 proportion of sand ; and that of a fine soft grit. Of 

 this class is the lime made from chalk, and all the 

 limestone of the Bahamas, the West India islands, 

 and the south west coast of this continent, which I am 

 told consists of immense rocks formed of shells, in 

 some instances very little changed from their original 

 state ; whereas our strong lime in Pennsylvania re- 

 quires a great proportion of sand, of a sharp grit, and 

 makes a very strong cement. 



I am- inclined to think, with Dr. Anderson, that 

 there is only one kind of calcareous matter ; and with 

 Dr. Darwin, that it has all originally been an animal 

 production ; that though the putrescent particles with 

 which it had been formerly combined, have long been 

 dissipated, it may still retain gases, which, when dis- 

 engaged, are nutritive to plants ; that pure calcareous 

 matters have little or nothing of a solvent quality ; and 

 that gypsum and lime derive their respective proper- 

 ties and additional value from the combination of cal- 

 careous matter with mineral acids, and other extrane- 

 ous substances. Hence I conceive, that if the pure cal- 



