220 Genetical Studies in Moths 



a different course. Probably influenced by the fact that efforts had 

 been made to bring the western end of the moor under cultivation in the 

 middle ages renewed attempts were directed towards the same end. As 

 advised in Marshall's Rural Economy^, a row of birches was planted 

 just within the northern boundary wall to act as a wind shield, and at 

 the same time the land was broken into fields. Failure once more 

 ensued as the soil composed of weathered Moor Grit is too light for suc- 

 cessful agricultural operations, and the plan was abandoned. In order 

 to avoid waste the " Intake " was then planted with larch and fir. Thus, 

 in the early " eighteen hundreds," Wilton Wood and Normanby Intake 

 Plantation were coniferous in character but included isolated clumps of 

 birch and alder, and this was exactly the position when the 1860 

 Ordnance Survey was made. If any difference is perceptible between 

 the two, it is that the latter wood is represented as being the more 

 closely provided with coniferous trees. 



By the very fact of the enclosures the alders along Skelton Beck and 

 around the Moorland Carrs were left exposed and have been destroyed, 

 only traces of their former presence being left. Thus early in the nine- 

 teenth century all communications between Wilton and Normanby 

 Woods via the alders of the moor pools and streams were broken. Never- 

 theless, conditions within the woods still agreed ; slope, elevation, ex- 

 posure, vegetation quite coincided ; the sole difference lay in the fact 

 that Wilton Wood lay on the geologically younger sandstones of the 

 Lower Estuarine series whereas Normanby Intake lay on the older Moor 

 and Fossiliferous Grits. 



Such agreement held until about the year 1885 when drastic changes 

 took place in the Intake Plantation. A heavy north-east gale so 

 damaged the trees that many broke off, and as the wood was ruined the 

 remainder were felled. When I first visited the wood in 1906 the decayed 

 stumps of those cut down still remained as did also the jagged trunks 

 of those hurled down by the wind. Except at the extreme south-east 

 (see Fig. 10) the only coniferous trees left were two seedling pines and 

 one larch. In their stead were springing up in all directions crowds of 

 birch saplings, obviously, from their north to south trend, proceeding 

 from those originally acting as a wind shield ; now (1919), almost the 

 whole area once under pine and larch is occupied by birch. Fully one 

 half of this ground has been gained since 1906. With this birch, around 

 the old pools still survive the alders of times long gone by. In contrast 



^ Marshall, Rural Economy of Yorkshire (1796). 



