18G4.] DR. T. STERRT HUNT ON PEAT. 427 



bogs, SO far as known, are chiefly confined to the plains along the 

 St. Lawrence and its tributaries, and appear to have been formed 

 in shallow lakes, which have been gradually filled up by a vege- 

 table growth. The peat often rests upon a layer of shell-marl, 

 which at one time formed the bottom of the lake. The vescetation 

 consists, for the most part, of mosses belonging to the genus Sphag- 

 num. Besides these, however, the bogs often support a growth 

 of tamarack (^Larix Americana), and of various ericaceous plants, 

 belonging chiefly to the genera Cassandra, Andromeda, Kalmia, 

 and Ledum. The leaves, roots, and stems of these help, with the 

 moss, to make up the peat. The peat near the surface of the bog, 

 consists of the moss but little altered, and is very soft and porous j 

 but in the older and deeper portions of the deposit it is more 

 dense and darker in color ; the vegetable tissue having undergone 

 a partial decay, by which its fibrous structure, to a great or less 

 degree, disappears, and the peat becomes earthy in its texture. 



These difi"erent forms of peat present very great variations in 

 their specific gravity. That from the surface of the Bog of Allen, 

 in Ireland, according to Sir Robert Kane, has a density of 0,335, 

 or only one third that of water ; while the blackish-brown earthy 

 peat, from a lower layer in the same bog, is from 0.639 to 0.672, or 

 double that of the surface. A peat which is dug near Tavistock 

 in Devonshire, has a density of 0.850. Similar difi"erences will 

 be found in the peat-bogs of Canada. A specimen of peat from 

 >Sherrington, described on page 642, is still more dense than any 

 of these, being so heavy as to sink in water ; while at the same 

 time it only contains 3.5 per cent, of ash. One of the great obstacles 

 to the use of peat is the large amount of water which it holds, 

 and the obstinacy with which it retains this water. The average 

 results of a great number of experiments made in the Irish bogs, 

 show that the general mass of the undrained peat, including both 

 the lighter and denser varieties, contains from 92 to 95 per cent 

 of water ; while the edges of the bog, and parts more or less 

 drained, in the state in which peat is generally cut, contain from 

 88 to 91 per cent. The turf, as used in that country, often holds 

 from 20 to 35 per cent of water; while that which has been 

 stacked from six to twelve months, still retains from 18 to 20 per 

 cent, and that which has been kept in a dry house for two years, 

 from 10 to 15 per cent of water. The above details, and many 

 of those which follow, are taken, in part, from Sir Robert Kane's 

 :work on " The Industrial Resources of Ireland," and a subsequent 



