FErvriLlTY OF THE GREEN-STONE SOILS. 265 



composition of serpentine we might be led to suppose that tlie coinpars- 

 live barrenness of the soils formed from it is due to the large quantity 

 of magnesia which this mineral contains ; and this may, in some cases, 

 be partly the cause. It would appear, however, that these soils often 

 contain very little magnesia, the long action of the rains and of other 

 agents having almost entirely removed it (see p. 209), and yet they stiil 

 retain their barrenness. But they contain no lime, and,, therefore, after 

 draining, the first great step to take in order to improve such soils, is to 

 give them a good dose of lime. How this step is to be followed up will 

 depend upon the effect which this treatment is found to produce. 



The soil of the green-stones is generally fertile, and it is more so in 

 proportion as the hornblende or augite predominates — that is, generally, 

 in proportion to the darkness of its colour. 



In Cornwall and South Devon, where scattered masses of trap occur, 

 consisting chiefly of hornblende and felspar, they "afford the most fertile 

 soils of any in the district when their decomposition has taken place to 

 a sufficient depth" (De La Beche). Wherever the trap rocks (locally 

 dun-stones) are observed at the surface, " it is deemed a fortunate cir- 

 cumstance, being a certain indicaiion of the fertility of the incumbent 

 soils." — [Worgan's View of the Agriculture of Cornwall, p. 10.] The 

 Miperior fertility of the neighbourhood of Penzance is owing to the pre- 

 sence of these rocks (Dr. Paris), and where their detritus has been mix- 

 ed wiih that of other rocks — as with the worthless granite soils — it ame- 

 liorates and improves their quality. 



. The same general character is exhibited by the trappean soils of other 

 districts of the island. The height of the Cheviot Hills renders the cli- 

 mate in many places unfavourable to arable culture, yet they produce 

 the sweetest pasture,* while the low country around them has been 

 largely benefitted by admixture with their crumbling fragments. The 

 whole of that lowland tract of Scotland, over which these rocks extend — 

 comprehending the counties of Ayr, Renfrew, Lanark, Linlithgow, 

 File, and portions of Perth, Sterling, Edinburgh, and Haddington, — ex- 

 hibit the fertile or fertilizing character of the decomposing green-stone. 

 In Cornwall it is dug up as a marl and applied to the land, and in the 

 neighbourhood of Haddington I have seen a farming tenant {a leasehold- 

 er) removing twelve inches of trap soil from the entire surface of a field, 

 for the purpose of spreading a layer of an inch in depth over twelve 

 limes the area in another part of his farm. There can be no doubt that 

 this mode of improvement is within the reach of many proprietors and 

 farmers — especially along the southern borders of Perthshire, and near 

 the more elevated of Ayr and Lanark. 



To the north of Ireland, and to the Western Islands, the above re- 

 marks, with slight modifications, arising from local causes, will also ap- 

 ply. For example, where the surface is flat, and the rock impervious, 

 water will collect and heaths and bogs will be produced, which only 



* It is a singular fact observed here and there among the Cheviot Hills on the border, that 

 where sheep are folded or pastured on hills of trap which are covered with delicate herbage, 

 they are attacked by what is locally called the pining iH,— they pine away, become indolent, 

 and are unwiUing to move. The cure is to drive them to a neighbouring sandstone pasture., 

 where they become again active, and begin to thrive. T)^e pining hills on each farm are 

 well known, and the tenant has no hesitation in pointing to this and to that hill as those Dn 

 which the sheep are sure to pine, if kept upon them only. 



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