320 



TRAVELS IN UPPER 



CHAP. XIX. 



Natron — Bleaching of cloth and thread — Other uses 

 of natron — Senna — Birds — Description of a spe- 

 cies of falcon Wagtail — Dragon-flies — Wasp- 

 Cricket — Rain — Delta — Herons — Coot — Quails 

 — Snipes — Armed plovers — Feme-greek. 



There arc in Rossetta magazines of natron, and 

 manufactures in which it is employed. It is well 

 known that this is an alkaline earthy salt, or 

 mineral alkali, found more particularly in Egypt, 

 in the middle of a desert, to which the ancients 

 gave the name of the Desert of Nitria, because 

 our saltpetre being entirely unknown to them, 

 they had given the name of nitre to that substance, 

 which the Arabs describe under the denomination 

 of natroum, from which we have derived natron. It 

 is from having neglected to examine the passages 

 of Theophrastus, of Dioscorides, of Galen, and of 

 Pliny, that several moderns h; ve confounded nitre 

 and rkatron, which are very d liferent substances. 



It is uncommon to meet with natron perfectly 

 pure. Besides the earthy matter which is almost 

 always mixed with it, it is not an entirely free al- 

 kali; it is usually united to marine salt, to Glauber's 



salt, 



