FOKE IGN COrtPvESPON DENCE . 



carbon, and non-crystalline. The sulpliur of tlie first category is that 

 extracted from combinations in which snlphnr enters as the electro- 

 negative element, as in sulphnretted hydrogen and the different 

 metallic sulphides. Tliat of the second category is extracted from 

 combinations in wliic-h it forms, on tlie contrary, the electro -positive 

 element, as in sulphureous acid, sulphuric acid, and their salts, &c. 



The sidphur we receiveel from Sicily is in large transparent crystals 

 belonging to the third crystalline sj'^stem, having for type the prism 

 with a rectangular basis, or, as the French crystallographers term it, 

 hi systems prlsmniiqiu' redaiiijiilairi' droit. It therefore is identical 

 with ]\r. Berthelot's octahedral or electro -negative sulphur; and, to 

 assure myself of this, I treated it with sulphide of carbon, and found 

 that it was completely soluble in this liquid, leaving not the slightest 

 residuum. Tliese natural crystals are, moreover, very beautiful, being 

 of a transparent yellow colou]\ and showing, here and there, in their 

 superficies or in their interior, the colours of the rainbow. 



It appears evident enough, from what we have just stated, 1st, that 

 this Sicilian sulphur has been crystallized in nature from a solution 

 and not by fusion — for sulphur, wlien crystallized l^y fusion, takes the 

 form of long prismatic needles belonging to another (the 5th) crys- 

 talline system (systemc jirl.-<m(itlqii(> ohtupie) ; its origin cannot, there- 

 fore, be inunediately attrilmted to volcanic eruption. 2ndly, that if 

 this sulphur be owing to the decomposition of any soluble combinations 

 in which this element enters, it must evidently have come from such 

 as contain it as an electro -negative element. For instance, from 

 sulphuretted hydrogen, or certain metallic sulphides, and not from 

 sulphurous acid, from sulphuric acid, or their salts. 



M. Lesquereux has read before the Societe de Neufchatel a paper 

 on the formation of i)rairies in America, which concerns at once 

 1)otanical geography and geology. The problem which the author 

 lias just endeavoured to solve, namely, the cause of the formation of 

 these vast American prairies, is as interesting to the geologist as to 

 the botanist, and, on this account, we will expose here the facts con- 

 tained in M. Lesquereux's memoir, which we consider most worthy of 

 notice. 



In nature, forests and prairies are not often met with smiultaneously 

 or intermingled one with the other, even on large portions of territory ; 

 on the contrary, tlvey are seen to stretch scjoarately over vast tracts of 



