796 DIGGING AND PREPARATION OF PEAT. 



bottom of the bog, pits 2 to 3 yards broad are dug, or a peat- 

 borer is used. 



Driving poles into bogs may lead to false inferences, if beds 

 of marl or trunks and stumps of trees, etc., are imbedded and 

 prevent the poles from reaching the bottom of the bog. 

 Digging pits is often impracticable owing to the accumulation 

 of water and always involves much labour and expense, but 

 this method affords the best possible insight into the nature 

 of the bog and must be employed to ascertain the quality of 

 the peat. It is best to use the peat-borer, as this generally 

 gives satisfactory results and saves much labour. Since, 

 however, few bogs are level at the surface and their bed is 

 often undulating and irregular, levels should be taken all 

 over the surface of a bog, the levels of the bottom and top 

 of each point of intersection being fixed with reference to 

 a horizontal plane through the highest point in the bog. 

 This levelling will show what is the contour of the bog, a 

 knowledge of which is requisite before its drainage can be 

 undertaken. 



(c) With the help of the above factors, the contents of the 

 peat-bog may be estimated in cubic feet. In order, however, 

 to estimate how much marketable peat there may be, a deduc- 

 tion must be made for shrinkage. For as soon as a bog has 

 been drained, it settles down and shrinks the more, the more 

 thorough the drainage. The amount of shrinkage must be 

 calculated by experiment. 



Thus pieces of peat of the ordinary dimensions are cut from 

 several trenches and thoroughly dried, their volumes being 

 calculated before and after drying and the difference between 

 them being the amount of shrinkage, which is generally from 

 30 to 50 per cent, of the volume of freshly cut peat. 



(d) Finally the loss of peat during extraction must be 

 estimated : this varies in quantity according to the skill of the 

 workmen, the quantity of stumps or stems of imbedded trees 

 and the cohesiveness of the peat, for the better kinds of peat 

 ,'iro much more brittle than inferior fibrous peat. 



During frosty weather in winter, the walls of the open peat- 

 trenches frequently crumble considerably ; besides this waste, 

 frequently ridges of peat remaining between the trenches 



