298 plint'3 natural histoet. [Book XXXV. 



tioned 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 and wool, for example, they 

 have been mentioned already.'^* 



CHAP. 53. (16.)— SAMIAN EAETH : THEEE EEMEDIES. 



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

 various other kinds of earth^^ which are made use ot m 



^OrS^mian earth there are two varieties ; one known as. 

 "collyrium,"3° the other by the name of - aster ' lo be m 

 perfection, the first kind should be fresh, remarkably smooth, 

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

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

 bv being calcined and then rinsed in water, some persons 

 giving the preference to the first. They are both ot them 

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

 ployed as an ingredient in plasters of a desiccative nature. 

 They are used also in the preparation of ophthalmic compo- 

 sitions. 



CHAP. 54. THE VAEIOUS KINDS OF EEETRIA. 



Of eretria, or Eretrian^^ 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^^ in our description of the pigments. 



CHAP. 55.— THE METHOD OF WASHING EAETHS 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 the beeinnin^ of this Chapter in part. 



29 ilumfnouf sihcates, as Delafosse remarks, more or less combined wi h 

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

 arenow hut little used in medicine. ^ i.„„^ nf +>,» fwn 



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

 in " colTyria;' or compositions for the eyes. 3i u gtar" earth, apparently 



•''2 From Eretria, in Enboea. See B. iv. c. 21. 

 33 In Chapter 21 of this Book. 



