252 History and uses of Peat. 



and plains, under alluvion formed by posterior deposits, and 

 indeed upon the sea shore under the sand. 



Peat beds are more or less compact or condensed; 1st, 

 according to the nature of the vegetables, the fragments of 

 which compose them, their trunks and stems being preserved 

 entire, or broken into fragments ; 2dly, according to the 

 greater or less thickness of the layer which is deposited, the 

 bottom of which is compact and condensed by its own weight 

 when it is thick, and looser when the deposit is inconsidera- 

 ble ; Bdly, according as there is, or is not, a superincumbent 

 stratum of alluvion over the mass of the peat. 



Peat beds are sometimes mingled with sandy, clayey, and 

 shelly deposits. Above peat beds, we usually find a bed of 

 marie or chalky clay. In some districts, this marie is much 

 used in agriculture. 



Several beds of peat are sometimes placed one above the 

 other, separated by deposits of sand, clay and earth. 



The thickness of peat beds is very variable, from six inch- 

 es, to twenty feet. 



Peat beds are ordinarily parallel to the deposits in the bot- 

 tom of valleys; and their direction is also that of the valley, 

 unless it has been deranged, or the formation of the peat has 

 been interrupted by a rapid stream passing through the val- 

 ley, or by some other cause which has an influence over the 

 water of the valley. 



We find in the work of De Luc, entitled A Letter upon 

 Men and Mountains, some interesting details upon the pro- 

 gressive accumulations of masses of peat, analogous to that 

 of glaciers in certain mountains. We have met, under cer- 

 tain beds in the valley of the Somme, with ancient cause- 

 ways, divers tools, and pieces of money. 



It would appear certain that peat beds are renewed, at 

 least in circumstances favorable to their formation. It is 

 however decided, that this renovation is a very slow process.* 



4. What are the means for discovering the existence of Peat? 



We may expect a valley to contain peat, when its surface 

 is extensive, smooth, and it contains stagnant waters, <jr those 



* It is probable tbat the peat beds of the United States, especially those 

 which have been worked near the sea coast, are derived principally from a 

 vegetable somewhat resembling moss ; and they are said to be renewed and 

 filled again within twenty or thirty years, a much shorter period than is taken 

 1<? reproduce them in France. — 2Vans. 



