256 



Yity of this matter, I put two- drachms of small iron 

 nails into three ounces of the water. After they had 

 Iain therein four and twenty hours, I found the sur. 

 face of the water covered with a thick scum, exactly 

 like that which usually covers a chalybeate spaw. I 

 observed likewise,!! had lost the blue colon r,.and sharp- 

 vitriolic taste. It was quite transparent, and at the 

 bottom lay a brown powder, which when dried, 

 weighed fourteen grains* This powder, molted with. 

 out any ilux, produced twelve grains of pure copper. 

 The nails also (which had lost eight grains) were 

 in several places covered with a solid lamina of pure 

 copper. The water being afterward filtrated and 

 evaporated, afforded a pure green vitriol. 



u 3. From the spring water treated in the same 

 manner, I obtained a blue vitriol, the basis of which 

 is copper. From ail the.se experiments it appears, 

 that a mineral acid is the active principle in this 

 water, which being diffused through the copper ore, 

 unites itself with that metal, and forms a vitriol. 

 This is dissolved by the water, and remains suspend- 

 ed therein, till it meets with the iron in the trough,, 

 and by which it is more strongly attracted than by 

 the copper. Therefore it quits the copper, corrodes 

 the iron, and changes it into a vitriol, which is again- 

 dissolved and carried off in the stream. Mean time the 

 copper, dv i sc:*.td by its acid, falls by its specific gra 

 vity to the bottom of the trough. 



44 It appears then upon the whole, that this ad- 

 mirable process of nature, whereby one. metal seems 

 to be turned into another, is no more than a simple 

 precipitation of the copper, by means of them/' 



In the Lower Egypt, there is a vast sandy desert, 

 calK-d the insert of St. Macarins. One large plain 

 herein is called by a uane which signifies the sea with, 

 out water. This is strewed over with limbs of trees 

 which are entirely petrified : very probably by means 

 of the i)itre ; with which this whole country abounds. 



