INDUSTRIES The procedure in quarrying granite is briefly as follows. A suitable position for opening a quarry having been determined on, the subsoil and loose and poor rock are removed. When this is finished, an examination of the joints is made, and the discovery of a good bed or hori- zontal joint determines the proper position for boring a hole to receive the explosive. The object is to dislodge a mass from its natural position with as little alteration as possible in its form, and it is therefore very important that all obstacles which might impede its free movement should be removed. Any neglect in this re- spect may result in the rock being shattered. It will therefore be understood that a great amount of judgment and experience is required to quarry successfully, and a hasty or ill- considered operation will most probably result in not only spoiling the rock to be moved, but also cracks may be developed in the rocks remaining in situ, and these may lead to trouble later on. When the rock has been dislodged by the successful firing of the hole, the quarrymen split it up into the smaller blocks to make the various-sized stones required. The splitting is accomplished by steel wedges inserted into numerous small holes drilled by hand across the various faces of the large rock, in such positions and in such lines as are determined by the experience of the quarryman. The dressing of the blocks for engineering works, as before mentioned, is done in the quarries ; but for building purposes, and for work which requires great care and skill, the dressing is usually done in the dressing yards adjacent to the shipping quays. Mention has been made of blondins as applied to the quarries. These lifting and transporting machines take their name from the famous acrobat and rope-walker who successfully ex- hibited his wonderful powers at Niagara Falls. The machine consists of a wire rope stretched across the quarry on which a carriage runs. This carriage can be made to travel to and fro on the rope by means of smaller ropes, which are controlled from a steam winch, conveniently placed so that the driver has an uninterrupted view of the quarry. The carriage has a lifting rope in connexion with it which is also con- trolled from the steam winch. Such machines command a very wide range, and as they are arranged to work at a high rate of speed they are particularly adapted to quarry work. It is well known that the tin industry of Cornwall has materially suffered from foreign competition. It appears likely that history will repeat itself, and the granite industry of the county will suffer in the same way. Of late years the vast resources of Scandinavia have been requisitioned. Abundance of granite is found there, in such positions and under such conditions that it is already proving a very formidable rival to the Cornish stone. SLATE QUARRYING The slate-quarrying industry of Cornwall has been of importance for at least three centuries, and especially during the last hundred years. Many efforts have been made to trace its history, but no authentic records of its commencement have been discovered. The earliest record found is that of Norden, who, writing in the year 1584, describes Menheniot slate as the best in Corn- wall. Carew, writing in 1602 in reference to Cornish roofing slate, is more explicit : ' In substance thin, in colour fair, in weight light, in lasting strong ; and generally carrieth so good regard, as (besides the supply for home provision) great store is yearly conveyed by shipping both to other parts of the realm and also beyond the seas into Brittany and the Netherlands.' 1 Borlase again, writing in 1758 of Delabole slate, says that for lightness and endurance of weather it is generally preferred to any slate in Great Britain, and is perhaps the finest in the world. Sir H. T. De la Beche, F.R.S., says Delabole quarries have long been celebrated for producing a beautiful and durable material combining con- 1 Carew's Survey of Cornwall, p. 20 (ed. 1811). siderable lightness with strength, and not liable to be damaged by frost. Delabole slate is described by Bishop Watson in his Chemistry as the very best in England. In 1865 Frederick Penny, Professor of Chemistry at the University of Glasgow, writes : ' I have made a scrupulous comparison of the Old Delabole slate with the Welsh, Highland, and Cumberland slates ; the results showing that the Old Delabole slate is of very superior quality. It is light in colour, thin and firm in lamination, close and compact in texture, extremely hard, and not easily worn by attrition. In strength and endurance of weather and friction it excels these well-known slates.' At the time of Borlase and De la Beche there were within six miles of Delabole many small quarries, but they were chiefly worked by small bodies of men. Most of them were worked for only a few years ; either the beds of slate rock were small and worthless, or the rock was so unproductive that it could only be worked at a loss. For some years past there have been only two quarries at work besides Delabole namely, Lanterden and Lambshouse. Both are in the parish of Tintagel. 519
