<240 usE 0F GREEN VITRIOL 



of iron. Thefe afhes, fays Mr. Gregor, " fteaded " * over 

 grafs apparently produced good effects notivithjlanding the 

 fulphate of magnefia, which I was well allured they contained. 

 See Nicholfon's Journal, Vol. V. p. 225. 

 Sulphate of From this obfervation of Mr. Gregor, it feems he is aware 



magnefia may qC lh prevailing popular opinion, that fulphate of magnefia 



not be hurtful , r >=> r r t r f ° .. 



n> plants, tho* is not favourable to vegetation; and to reconcile his tact with. 



purema 6 neaa t t, e un f r j e ndly nature of magnefia to plants, as difcovered by 

 Mr. Tennant, he obferves that the effeds of fulphate of 

 magnefia may be very different from thofe of magnefia and 

 carbonate of magnefia. I apprehend it is the magnefia (cal- 

 cined magnefia) only which this learned chemift found hurtful 

 to vegetables, as the difcovery was made on the examination 

 »f Nottingly lime, which the farmers near Doncafter employ 

 as a manure, while they rejeft the lime of their own neighbour- 

 hood. In the latter Mr. Tennant met with magnefia, and in 

 the former none. See the account of this important difcovery 

 in the Philof. Tran factions. 



2. The Earth from 4/kes called Cims, is a durable and efficacious 

 Manure; hj Proftfor Mitchill, of New York, one of the 

 Ueprefnlatives in Cougrefs. AddreJJ'ed to Dr, Pearfun. 



Earth from athes Dr. Mitchill, in a letter addreffed to me on cims, or earth 

 is a good manure, |- ound j ft ^ aflies Q c w00( ] f nas m ade fome obfervations rela- 

 tive to the preceding memoir, which feem worthy of notice. 



«' A (lies of wood contain very commonly fulphate of potafh, 

 alfo phofphoricacid, betides other well known falts ; but after 

 thefe falts are feparated by lixiviation, there remains a peculiar 

 earth, and a fuiall proportion of iron. This earth differs from 

 iime, baryt, magnefia, ftrontian, or any other known fpecies 

 of earth. I would call it cinrs, for plentiful, common, and 

 important as it is, fcience has not dignified it with a name. 

 To judge of the excellence of this earth as a manure, after 

 all the falts are exlrafted from foap boilers' allies, the earth 

 felfe for ten cents the bufliel, and notwithstanding this high 

 price, it is not unufua! for the farmer to pay for the article 

 twelve months beforehand. When ploughed into fterile 

 ground, at twelve loads per acre, it produces great crops cf 

 wheat, clover, and other forts of grafs and grain, and its 

 fertilizing operation will laft twenty years. Although fome 



• From ^KiSax, 



of 



