VEGETABLE FOSSILS. 



When vegetable matter, grass for instance, is accumulated 

 in so large a quantity that the compactness of the mass 

 may in a great degree exclude the atmospheric air from the 

 internal parts of the mass, a considerable and peculiar 

 change is effected : the vegetable matter soon loses its 

 green and acquires a brownish colour ; its flavour and odour* 

 are changed, and heat is produced, terminating, unless air 

 is freely admitted, in combustion. The vegetable matter, 

 thus changed into Hay^ acquires, among its other new 

 properties, that of powerfully resisting any further change 

 upon exposure to the atmosphere. 



But should vegetable matter be thus accumulated in a 

 situation in which moisture has almost constant access to 

 it, a very different result ensues. Another process takes 

 place, by which the vegetable matter, as the process goes 

 on, loses its original forms, and becomes a soft magma, of a" 

 dark colour and peculiar appearance ; no traces of its 

 former mode of existence being discoverable, except in the 

 accidental presence of such vegetable matter as shall not 

 have undergone a complete conversion. When dried, it 

 forms a readily combustible substance, of a reddish brown 

 colour, readily absorbing and tenaciously retaining water, 

 and yielding, whilst burning, a strong bituminous odour. 

 This is the substance termed peat, immense accumulations 

 of which are formed in various parts, favourable to the col- 

 lection of water and the growth of the sphagnum palustre, 

 a plant, by the conversion of which the supply of this 

 substance is chiefly supported. In the peat-bogs or mosses, 

 as the natural magazines of this substance are called, trunks 

 of trees are often found imbedded, and partaking of the 

 nature of the surrounding bituminous mass. This change is 

 effected in different degrees : the deeper in the mass, and 



