ON PARING AND BURNING GRANITE SOILS. 39 



prized ; the lower portions, condensed by the superincumbent weight, 

 becoming a much more effective fuel. 



Springs commonly break out from these bogs, as though superficial 

 to the stone ; but there are instances of a different kind : on the 

 eastern foot of Ugborough-beacon, is a fine spring pouring out of the 

 rock probably two hogsheads a minute. Such as these may perhaps 

 owe their origin to another condition of the granite, where the crystals 

 of quartz and felspar are incoherent, and the schorl has very much 

 disappeared, forming a sort of gravel many yards in depth. Such a 

 bed of great extent lies on one side of Hessary-tor, near the prison. 



In wood this rock appears to be unproductive. A few young planta- 

 tions of fir do not yet appear to suffer more than might be expected 

 from the climate ; some fine trees are found about the borders of the 

 streams; and trunks of considerable dimensions have been dug up 

 from the bogs : but it is said by gentlemen possessing estates on the 

 granite, and my observation agrees with it, that trees, after reaching a 

 certain height, rise no farther ; spreading and twisting their branches 

 without proportionate increase of trunk. Wistman's wood, a plot of 

 oaks, supposed to be of a thousand years' standing, the largest less 

 than a man's waist, and within twenty feet high, is an extreme 

 instance. 



The outline of the granite, from Tavistock to Hey-tor, southward, 

 may indeed be almost traced by the coppice, which, clothing the 

 declivities of the slates and other rocks that abut against it, disappears 

 suddenly on its gritty soil. 



ON PARING AND BURNING GRANITE SOILS, AND OTHERS, 

 WHERE CARBON IS DEFICIENT. 



BY THE EDITOR. 



THE remarks in the foregoing paper, on the infertility of the soil in 

 granite districts, has suggested to me a probable remedy for this ; and 

 though our Magazine is not intended to embrace the practice of culti- 

 vation, it will always be open to papers tracing the causes of success, 

 or the contrary, in field and garden operations. 



It is now pretty generally agreed upon, I believe, that carbonic acid 

 gas diffused through water is the principal, though not the only food 

 of plants; and, consequently, where this is deficient any soil will be bar- 

 ren, such as that where the base is the debris of granite, or other rocks 

 containing little or no carbon. This view is strongly corroborated by 



