172 On Gypsum. 



If it IS, it acts by its septic quality, when applied in small 

 quantities. It prevents the operation of plaister, by fur- 

 nishing soda to the acid of the gypsum; and with it 

 forming sulphat of soda, fglauber salts.) This is the 

 cause of the plaister not operating on sea coasts. I have 

 ruined a bushel of plaister by an handful of salt; which 

 renders it unfit either for manure or cement. 



It is of no farther consequence to the farmer to know 

 the operative principle of the plaister, than as it directs 

 his practical use of it. And whether it acts per se di- 

 rectly, or by the disengagement of other acids, by its 

 means; when it expels them and takes their places, is 

 immaterial; if the results are attended to. The viodus 

 operandi of manures, is a complicated and yet unsettled 

 subject. It is highly probable at least, in theory, and 

 practical results confirm it, that there is in the earth, 

 assisted by the atmosphere and waters, some process, 

 or resolvents, to set free this potent actor ; either for its 

 own operation, or to disengage other acids beneficial to 

 vegetation. The laboratories of the chymists are inca- 

 pable of establishing indisputably, or confuting satis* 

 factorily, this position. The fields of the farmer exhi- 

 bit agricultural facts, by which it has been sufiiciently 

 tested for his purposes. By these he is enabled to 



benefits in husbandry. It contains, in a ton, a bushel or a 

 bushel and an half of salt. Sea salt is recommended for the 

 destruction and putrefaction of snails, slugs, grubs, -worms 

 raid insects infesting grounds. They abound the most in 

 lands to which animal manures have been long applied. The 

 vitriolic acid is equally efficacious ; and I have therefore be- 

 lieved, they do not so much infest plaistered fields. 



