AFFOEESTATION OF PIT MOUNDS 69 



did not look very promising for tree growth. A shovelful 

 of good soil put in round the roots at the time of planting 

 greatly assisted the growth of the young trees at the start. 

 Mr. Cadell believes that in many districts pit banks, especi- 

 ally those at abandoned mines where there is neither smoke 

 nor mischievous people to injure the trees, may be planted 

 with a view to profit. Mining districts are usually provided 

 with railways, and furnish a good market for any timber 

 that is grown locally. 



The immense shale banks around the oil works in West 

 Lothian and other districts are diflicult to plant. If iron 

 pyrites is present, the sulphuric acid formed when the shale 

 is decomposed prevents the growth of any vegetation. Mr. 

 James Whittou instances shale bings forty or fifty years old 

 at Nitshill in Eenfrewshire on which not even a blade of 

 grass has appeared. Some of the oil shale, however, sup- 

 ports plant growth fairly well, as is evident near Linlithgow, 

 where Mr. Cadell has noticed the appearance of natural 

 vegetation on abandoned bings. The latter might be planted 

 with grey alder, black Italian poplar, etc. It must not be 

 forgotten that the fumes from shale works are deleterious to 

 the growth of trees, the effect being especially grave when 

 sulphuric acid required for refining is manufactured at the 

 works (8). 



On an extensive slag heap at Quaregnon, in Belgium, 

 planted up in 1891 with Robinia, alder, elm, birch, horn- 

 beam, ash, sycamore, horse-chestnut, laburnum, etc., the best 

 species appears to have been Robinia, which in eighteen 

 years after planting had attained as much as three feet in 

 girth. On another large slag heap, planted 25 years, 

 hybrid black poplar was also three feet in girth. M. C. 

 Leonard, who gives an account of these plantations in 

 Annales de Gembloiix, Oct. 1909, recommends that, after 

 weathering for eight or ten years, a heap should be covered 

 first with herbage by sowing seeds of grasses, lucerne, 

 sainfoin, etc., and afterwards be planted up with 3- to 

 4 -year-old transplants of Robinia, birch, grey alder, Pnmus 

 serotitia, sycamore, and Qicercus rubra. 



