8o TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



Steam-plough culture it is now, he states, the rule that areas 

 operated upon should lie fallow for a period including at least 

 two winters, in order to restore the capillary activity of the soil. 

 The sample plots of steam-plough operations examined by 

 Dr Albert had not been treated in accordance with the most 

 approved and now generally adopted method. 



Dr Albert, in his final report on the researches he made in the 

 course of several years in the Luneburger heather tracts, now 

 explains that the conditions of the soil are abnormal over 

 extensive areas, and that the use of the steam-plough is the only 

 means of dealing with them. 



The sandy soils of the heather tracts, the only ones which are 

 still available for aflforestation, are, he states, found in two 

 entirely distinct varieties, which, in accordance with the 

 characteristic colour of their upper layers, may suitably be 

 designated as grey and brown heather sands. The former are 

 clearly pronounced bleached-out soils, though varying consider- 

 ably in depth and the amount of humus they contain. A 

 stratum is almost invariably found below these bleached sands, 

 bound together by particles of soil washed out of the surface 

 layers. The colour of this stratum varies considerably from 

 rust-red to a deep brown-black, and so does the intensity of 

 adhesion amongst the different particles, from friable Ort soil 

 to a solid Ortstone formation. 



In diluvial sands such strata are found with great consistency 

 about 30 cm. below the surface, though in alluvium the depth 

 may be considerably larger. All that is known about the origin 

 of this peculiar formation is that it is invariably found on a 

 basis of a compact layer of waterworn stones, chiefly flint and 

 quartz, the intervals between which filled with a schistose sand 

 forming an impenetrable bar between the upper and lower 

 parts of the soil. Such strata, though only about 10 cm., or rarely 

 up to 15 cm. thick, must naturally interfere with the movement 

 of water in the soil and encourage the deposit of sediments on its 

 surface. The brown heather sands are, on the contrary, entirely 

 normal ; there are no signs of a bleaching process in the surface 

 soil, the change towards the lower strata is gradual and 

 uninterrupted by any such strata as underlie the Ort formation. 

 These brown sand tracts have unquestionably been under 

 heather for centuries, as long as the grey sands, but are to-day 

 perfectly sound. This seems naturally to lead to the theory 



