B. _Fibrous peat_, unripe peat, which is brown or black in color, less elastic than turfy peat, the fibres either of moss, grass, roots, leaves, or wood, distinguishable by the eye, but brittle, and easily broken; sp. gr. 0.24 to 0.67, the weight of a full cubic foot being from 15 to 42 lbs.
C. _Earthy peat._--Nearly or altogether destitute of fibrous structure, drying to earth-like masses which break with more or less difficulty, giving lustreless surfaces of fracture; sp. gr. 0.41 to 0.90, the full cubic foot weighing, accordingly, from 25 to 56 lbs.
D. _Pitchy peat_, (_Pechtorf_,) dense; when dry, hard; often resisting the blows of a hammer, breaking with a smooth, sometimes lustrous fracture, into sharp-angled pieces. Sp. gr. 0.62 to 1.03, the full cubic foot weighing from 38 to 55 lbs.
In Kane and Sullivan's examination of 27 kinds of Irish peat, the specific gravities ranged from 0.274 to 1.058.
3.--_Heating power of peat as compared with wood and anthracite._
Karmarsch found that in absolute heating effect
100 lbs. of turfy, air-dry peat, on the average = 95 lbs. of pine wood. " fibrous " " " = 108 " " " earthy " " " = 104 " " " pitchy " " " = 111 " "
The comparison of heating power by bulk, instead of weight, is as follows:--
100 cubic ft. of turfy peat, on the average[12] = 33 cubic ft. of pine wood, in sticks. " " fibrous " " = 90 cubic ft. of pine wood, in sticks. " " earthy " " = 145 cubic ft. of pine wood, in sticks. " " pitchy " " = 184 cubic ft. of pine wood, in sticks.
According to Brix, the weight per English cord and relative heating effect of several air-dry peats--the heating power of an equal bulk of oak wood being taken at 100 as a standard--are as follows, _bulk for bulk_:[13]
_Weight per _Heating cord._ effect._ Oak wood 4150 lbs. 100 Peat from Linum, 1st quality, dense and pitchy 3400 " 70 " " 2d " fibrous 2900 " 55 " " 3d " turfy 2270 " 53 Peat from Buechsenfeld, 1st quality, pitchy, very hard and heavy 3400 lbs. 74 Peat from Buechsenfeld, 2d quality 2730 " 64
These statements agree in showing, that, while weight for weight, the ordinary qualities of peat do not differ much from wood in heating power; the heating effect of _equal bulks_ of this fuel, as found in commerce, may vary extremely, ranging from one-half to three quarters that of oak wood.