298 PLIXY'S >MTUKAL HISTORY. [Boo 



tioncd as being treated with the other kinds of alumen, that 

 imported from Melos, be it understood, is still more efficacious. 

 As to the other uses that are made of it for industrial pur- 

 poses, such as preparing hides azid wool, for example, they 

 have been mentioned already. 28 



CHAP. 53. (16.) 8.VMIAN EAUTH : THIIKE ItKMKDIKS. 



In succession to these, we shall now have to speak of 

 rarious other kinds of earth'-* which are made use of in 

 medicine. 



Of Sumian earth there are two varieties ; one known as 

 "collyrium," 30 the other by the name of " aster." 31 To be iu 

 perfection, the tirst kind should be fresh, remarkably smocih, 

 and glutinous to the tongue; the second being of a more 

 solid consistency, and white. They are both prepared for use 

 by being calcined and then rinsed in water, some persons 

 giving the preference to the tirst. They are both of them 

 useful for discharges of blood from the mouth, and are em- 

 ployed as an ingredient in plasters of a desiccativo nature. 

 They are used also in the preparation of ophthalmic compo- 

 sitions. 



CHAP. 54. THE VARIOUS KINDS OF ERKTKIA. 



Of eretria,or Eretrian 32 earth, there are also the same number 

 of varieties ; one white, and the other of an ashy colour, this, 

 last being preferred in medicine. To be good, this earth 

 should be of a soft consistency, and when rubbed upon copper 

 it should leave a violet tint. The virtues of eretria in a medi- 

 cinal point of view, and the methods of using it, have been 

 already mentioned^ 3 in our description of the pigments. 



CHAP. 55. TRE ilETUOD OF WASHING EARTHS FOR MEDICINAL 



PURPOSES. 



All these earths for we will take the present opportunity 

 of mentioning it are well washed in water, and then dried 



2 * At tlie beginning of this Chapter in pnrt. 



29 Aluminous silicates, as IMatossu remark*, more or less combined \vith 

 other minerals. Though employed for various purpose* in the arts, they 

 are now hut little used in medicine. 



Jy Probably because it was the more extensively employed of the two, 

 in ** collyria," or compositions for the eyes. 3l u Star'* earth, apparently 



S2 From Ert'tria, in Eulxi-a. Sec B. iv. c. 21. 



w la Chapter 21 of this liook. 



