<>:26* MAG&KSIAN earth: 



com " ^ the . aeid as the eailh of BaudifTero. In a word, it is' completely 

 earth of Baudif r * l J 



fero, with the the lame as this laft, with this foie difference, that phyfically 



fmall difference confidered it is lefs compacl. and becomes even friable, and 

 noticed, • , . ,, ,-,,.. . , ■ ,.-, 



chemically confidered it contains a fitfle more (ilex. 



It appears then to be well proved that the earth of Bau- 

 ditTero and that of Caftellamonte are each a true native mag- 

 nefia, mixed with a little fii-.v. In the earth of Caftellamonte 

 it is fufficiently demonftrated that it contains no carbonic acid 

 Vvhen in the bofom of the earih; and that it only contains it 

 when, after a long expofure to contact with the air, it can 

 abforb it from the atmofphere. That of BaudifFero contains 

 Earth of Bau» m truth carbonic acid, 'but tiie quantity is much inferior to that 

 differo has not which it ought rceceflari.'y to contain to be confidered a carbo- 

 be' carbonate of nate °^ magnefia ; befides the earth of Baudiffrro having been 

 magne/ia. worked for a longtime, and Befog thus in contact with the air, 



it is from the atmofphere it mud have drawn it, and tltil in 

 If dug from a proportion to the time it has been expofed ; at leaft I have no 



fufficient depth doubt that if the earth of Bouciiffero was dug up from a cer- 

 would probably A . . . . . . , , , , ., . . . 



contain no car- ^in depth, no carbonic acid wowd be found in it. 



bonic acid. I vvill conclude this addition to the memoir, by obferving 



lette probably" that the earth of Mufinet at Cafe'ette, being produced by the 



magnefian a!fo. decompotition of the fame Corneen ftone or Cacholong, ought 



alfo probably to be a magnefian earth; bat I have not yet 



made any experiments en this earth ; Doctor Bonvoifin, who 



has given the analylis of it in its ftate of Cacholong and Hy- 



The author pro drophane ftone, propofes in conjunction with me to repeat the 



pofes to analyfe analyfis of this ftone, in the true ftate above-mentioned, and 



Hytopwf in itsearth y ftale 5 vvbich fha11 be the (bb i ea of a Particular 



and write a me- memoir.* 

 moir of the re- 



* The laft ttfe which Mr. Giobert mentions, for magnefian earth 

 }s of the moft confequence of the two, for as fulphate of magnefia 

 is only ufed in medicine, the fale could not be fufficiently extenfive 

 to produce much profit on a large fcale. 



The ufe of this earth for pottery is the more deferving of notice, 

 as it has hitherto been fuppofed that argil was alone proper for this 

 purpofe ; and though it was long known that magnefia is of a v«ry 

 refractory nature in the fire, Mr. Giobert feems to be the firlt who 

 thought of ufing it in crucibles ; which is the more extraordinary, 

 as the lapis ollaris, which derives its name from its property of ferv- 

 ing to make utenfils to bear the fire, is well known to contain a 

 large proportion of magnefia. 



5 As 



