The natural product of the high lands is only a thin turf interspersed with heath, fern and furze,[35] and many huge blocks of granite are disseminated in all directions; this circumstance has materially impeded the progress of cultivation, for in order to remove these _boulders_ it is necessary to blast them with gunpowder; the fragments, however, become useful in their turn, and are employed in making enclosures, which bear the provincial name of _hedges_. This stone, commonly called _Growan_, is, moreover, wrought into columnar masses, eight or ten feet long, which are used as supporters to sheds and outhouses, or gates posts, and bridges over rivulets. It is also the material of which common rollers, mill-stones, salting and pig troughs are made; in short, few stones are converted to more various purposes of rural oeconomy, and it accordingly forms an article of some commercial value. The mode of splitting it into the required forms is somewhat curious; it is effected by applying several wedges to holes cut, or _pooled_ as it is termed, in the surface of the stone at the distance of three or four inches from each other, according to its size and hardness; the harder the mass, the easier it may be split into the required form; the softer, the less regularly it separates. The blocks of granite employed in the construction of the Waterloo Bridge over the Thames were procured from the downs in the vicinity of Penhryn.[36] The Granite of the Land's End district is remarkable for its coarse grain, and the large proportion of its felspar, which, according to the observations of _Dr. Paris_, may be estimated as high as from 70 to 90 per cent. It moreover possesses an earthy texture, which greatly accelerates its decomposition. This circumstance will in some measure account for the unusual fertility of the _growan_ soil in the parishes of Saint Burian, Sennen, and Saint Levan. It will moreover explain the theory of a practice, which would otherwise appear absurd, that of actually applying the disintegrated _growan_ to certain lands as a manure! On a closer examination of this Granite, the prismatic crystals of felspar will often be found to exhibit that structure which _Haüy_ calls _hemitrope_; more often, they are termed _macles_, and are compounded of two crystals intersecting each other at particular angles. The Botanist as he rides along in the Summer months will observe amongst the gorse (_Ulex_), which is abundant on each side of the road, the parasitical plant _Cuscuta Epithymum_, (called _Epiphany_ by the country people,) winding its spiral structure in all directions, and producing from its reddish hue a beautiful contrast.