STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 23 



Peat. 



Peat is the familiar accumulation of more or less changed vege- 

 table matter observed in localities sufficiently moist. It is most 

 abundant in Pleistocene and Recent deposits, but a very similar 

 material occurs in the Tertiary and, even in the Carboniferous, one 

 finds a substance, which in hand specimens can hardly be dis- 

 tinguished from well-dried peat. 



Conditions Requisite for Accumnlation. — As asserted long ago 

 by Alex. Brongniart, constant supply of moisture in considerable 

 quantity is a prerequisite for growth of peat. Ponds and shallow 

 lakes in glacial drift have been favorite localities in the northern 

 part of the temperate zone, where deposits vary in extent from a 

 few square rods to several scores of square miles. Areas of deep 

 water are made shallow by accumulating animal and vegetable 

 remains, largely of humble types, and eventually become filled with 

 normal peat. But such deposits are, individually, of small extent, 

 though they are so numerous that, collectively, they cover much of 

 the formerly glaciated surface within North America and Europe. 

 Peat areas of greatest extent are those originating on coastal plains 

 or on those bordering rivers, where the sluggish drainage is checked 

 readily by petty obstacles and small patches of swamp become united 

 until a great space has been occupied. Some deposits of this type 

 have an area of many hundreds of square miles. 



Peat has provided fuel for much of northern Europe during cen- 

 turies and the literature with reference to it is voluminous ; but it 

 has no economic importance within the tropics, so that definite 

 statements respecting its occurrence are comparatively few. Ex- 

 plorers naturally were concerned more with geography and anthro- 

 pology, so that one finds usually little aside from incidental state- 

 ments to the effect that a region is swampy, boggy and difficult to 

 traverse. But more than one hundred years ago, Jameson- stated 

 that Anderson had received peat from Sumatra. Certainly the 

 conception that true peat is confined to the temperate zones is 

 erroneous. Livingstone in 1858 and 1866 presented abundant evi- 



- R. Jameson, " An Outline of the Mineralogy of the Shetland Islands, 

 and of the Island of Arran," Edinburgh, 1798, pp. 151-153. 



