192 DESCRIPTIVE MINERALOGY. 



often of great beauty ; but after a short exposure to the air, they are usually converted into 

 sulphate of iron. The stratum of lignite is imbedded in a dark blue astringent clay, which 

 contains a large proportion of pyrites in nodules and grains. When this is exposed to the 

 air for a time, it acquires a green efflorescence of sulphate of iron. 



Lignite occurs with similar associates in various parts of Suffolk county ; but neither here, 

 nor in Richmond, has it been found in quantities suiBcient for fuel. 



So far as my observation extends, the masses of lignite are accompanied by fragments of 

 wood which have undergone no alteration whatever, except what may be ascribed to the me- 

 chanical action of the water to which they are constantly exposed. 



A minute examination of the Rossville locality has satisfied me that the change of this drift 

 wood into lignite is due to the action of sulphuric acid contained in the clay, so similar are many 

 of the specimens in their appearance to the charred vegetable matter found at the celebrated 

 sour spring in Byron, Genesee county. I subsequently ascertained that the same view had 

 been broached by Dr. Emmons, in a notice of the lignite of New-Jersey. The facts which 

 he adduces in its support are, 1st, that the charring seems to be of recent occurrence; 2d, 

 that there is a difference in the change which different fragments have undergone, from being 

 unequally exposed to the action of the acid ; 3d, that free sulphuric acid may be detected in 

 the small streams flowing down the banks, produced by the decomposition of the iron pyrites ; 

 and 4th, That the charring is most perfect where the pyrites is most abundant, and where 

 this mineral is wholly wanting, no carbonization is perceptible.* 



This interesting process, as above suggested, has no doubt taken place recently, and is 

 indeed perhaps daily going forward. The sulphuric acid or acid sulphate of iron contained 

 in the clay, acting upon the strata of drift wood which are thrown upon the bank, causes 

 a partial or entire carbonization. The carbon thus formed, again reacts upon a portion of the 

 sulphate, and by abstracting its oxygen, gives rise to iron pyrites or peroxide of iron, depend- 

 ing upon the extent to which the decomposing action has been carried. 



It is worthy of notice, also, that small masses of amber arc found associated with the lignite. 

 As this mineral has been proved by Sir David Brewster to be of vegetable origin, and is per- 

 haps the hardened juice of certain trees, can its formation be ascribed to the same cause to 

 which that of the lignite has now been referred ? 



I will only add, that localities of lignite have been noticed in Dutchess and Columbia coun- 

 ties, by Mr. Finch ; and by Dr. Emmons, in those of Essex and Warren. 



PEAT. 



Peat. Ckavckind. — Tourbe. Bendant. — Turf of the English. — Torf of t/ie Germans. 



Description, Colour brown, sometimes yellowish or reddish, or dull black. It has a loose 

 texture, more or less porous, or even spongy. When recently dug, it forms a viscid slimy 

 mass, which, by exposure to the air, becomes dry, hard, and more or less brittle. 



* American Journal of ScieTice, XXIII. 371. 



