144 VEGETABLE SUBSTANCES. 



for the growth- or for producing excellence in the 

 quality of these tuberous roots. 



When cultivated in tenacious argillaceous soils, if 

 the summer be dry, the swelling of the tubers is pre- 

 vented by the mechanical pressure of the earth ; and 

 on the other hand, such soils, if kept constantly in a 

 state of moisture, produce immature tubers, which 

 are sodden, waxy, and otherwise of bad quality. 

 But in ground which to all appearance is little else 

 than loose sand, if there be humidity enough, pota- 

 toes will grow and be of excellent quality, and, even 

 should there be any failure in the sufficiency of 

 moisture, the quality of roots yielded by the first 

 planting will be good, but they will be small, and 

 too hard for propagating. In the mountain dis- 

 tricts of Scotland the frequent rains in all seasons 

 are of so constant recurrence, that a whole week of 

 dry weather is considered worthy of record. This 

 circumstance, so unfavourable to the maturity of 

 other crops, operating in union with the peculiar 

 nature of the soil, causes the situation to be well 

 adapted to this cultivation : while there are still 

 other advantages on the west coast of the Scottish 

 Highlands, and which apply in a great measure to 

 Ireland. In the first place there is very little frost 

 never any except in high and comparatively inland 

 places until the potatoes are come to their proper 

 growth. Again, spade husbandry is best adapted 

 for potatoes, and it is also the best for those places, 

 where the acclivities are generally too abrupt, and the 

 spots of land really worth culture too small to admit 

 of the use of the plough with any advantage. Per- 

 sons who are acquainted with only flat countries, 

 where there is little inequality of soil in a field, and 

 no absolute sterility in a parish, but that which is 

 consequent on neglect, can form but an imperfect 

 idea of the variations witnessed in a little portion of 



