22(J SULPHATE OF MAGNESIA. 



abrownifh hue. I gradually evaporated itftill further, and (et 

 it afide in a cool place: It (hot into a beautifully cry ftallized 

 fait, which agreed in form and properties with U)e pureft ful- 

 phate of magnefia, except as to colour, which inclined to- 

 wards a brownifh tint, which circumftance probably arofe from 

 the extractive matter of the decayed wood, which this fait had 

 penetrated. The coals, which had been lifted in this place, 

 were thofe from Liverpool and Wales. The place was open 

 to the air and rain. 

 Liverpool coal I" order to narrow my field of conjecture as to the origin of 

 treated more tj ie above-mentioned falts, and to exclude, as far as pofiible, 

 a^purer refult. " tne concurrence of unknown circumftance?, I collected a fuf- 

 ficient quantity of allies from my own fire in my ftudy, where 

 I had burnt Liverpool coals only. On repeating the fame pro- 

 cefs, the refult was the fame : I obtained gypfum and a ftill 

 purer fulphate of magnefia : The quantity of the latter ex- 

 Welch coal alfo. ceeded that of the former. I examined alfo the allies pro- 

 duced by Welch coal, and I detected gypfum and the fulphate 

 of magnefia in them alfo. They contained, however, a much 

 larger quantity of gypfum than of the latter fait. 



The exact quantities of thefe falts, which might be obtain- 

 ed from a given weight of the allies of thefe different coals, 

 I did not a/certain. 

 Thefe aflies The aflies obtained from the above-mentioned coals were 



were a good ™- fr om t ; me ^ t j me fpread, (or to ufe our common and provin- 

 cial term) Jkeaded * over grafs, and with apparently good ef- 

 fects, notwithftanding the fulphate of magnefia, which, I wa» 

 well affured that they contained. 

 Mr. Tennant Mr. Tennant's difcovery of the unfriendly nature of magnefia 



LfiasHid iti *° ve g etat i° n IS to De ranked amongft the few prominent and 

 carbonate are in- well eftablilhed facls in agriculture, which modern fagacity 

 lmical to vege- ^as b roU ght to light. Communications of fads and difcoveries 



tation* but the . .... . . . r • • i , r 



fulphate may in this highly important tcience are, indeed, abundantly lup- 

 be good. plied unto us by ingenious and experienced agricultures, but 



the truth and the utility of the greater number of them mull, 

 from the nature of the fubjeel, depend upon fuch a variety of 

 variable circumftances, that the application of them to parti- 

 cular cafes can be only contidered as a matter of experiment. 

 But Mr. Tennant's obfervations, contained in his effay on the 



* Etymologifts may probably recognize in this word the Greek 

 verb Zk@ccv, 

 5 different 



