150. The principal centres in Scotland of the granite industry in connection with supplying material for the making and repairing of roads and streets are Aberdeen, Cove, Kemnay, Peterhead, Dalbeatie, Bon Awe, Furnace Quarries (Loch Fyne), Kilsyth, and in Kincardineshire. Paving setts and kerbing are produced from these quarries in large quantities, and are much used in the principal cities of Scotland and in many parts of England. Road metal of this material, however, is used only to a limited extent, and that generally in the vicinity of the quarries mentioned. At times, however, a considerable demand exists for the better qualities of granite-macadam in some of the large towns within reasonable distance of the source of supply. Most of the counties are well supplied with suitable rock for producing road metal, such as basalt and whinstone, and the majority of the quarries are worked under the direct control of the County Councils. Previous to 1892, under the Road Trustees a similar arrangement existed, and was, until recent years, worked on the contract system at an inclusive price per cubic yard. Of late years, however, every effort has been made in many counties to secure the utmost economy by the authorities working their own rockdrills, and by the surveyors personally superintending the quarrying operations in their respective districts and counties.

151. In Ireland granite is largely quarried in the counties of Armagh, Down, and Wicklow, while basalt and whinstone are readily obtained and largely made use of for road purposes in the counties of Antrim, Donegal, Down, Londonderry, and Tyrone, limestone forming one-half of the material used for macadam.

152. As bearing on the subject of supply and demand for cheap and durable materials for macadamizing roads and paving streets, it seems strange that, with an abundant supply of suitable rock for the purpose, this country, especially the counties on the south and east coasts, is threatened with com. petition of a permanent nature for supplying these materials from France, Belgium, and Norway. As a matter of fact, there are annually imported into this country large quantities of Belgian and Norwegian macadam and paving setts, which, no doubt, are of good quality, while the price per cubic yard or ton is considerably less than for similar material from Mount Sorrel and the other quarries in Leicestershire. The effect of railway carriage on the price of these materials seriously threatens the stone industry of certain counties in this country, and any means by which the cost of land-carriage can be lessened, and

the working expenses reduced in the production of paving setts, and macadam for making and maintaining roads, should be carefully studied. Therefore, any expedient by which retrenchment, however small, is possible, should be practised by the judicious employment of modern plant and machinery for manipulating and transporting the material, and, no doubt, would result in large sums of money being saved.

It is estimated that 2 million tons of material are used annually for road stone and paving in these islands; the cost of the quarried rock alone amounts to about £130,000; while the value of the finished material is over half a million sterling.

CHAPTER V.

QUARRYING.

153. In the preceding chapter the quality of the rock necessary for preparing road metalling and paving setts has been explained. The methods of procuring or quarrying the material will now be described, while the cost of the operations, depending on many considerations, will be entered into in detail.

The igneous rocks are found in irregular masses and dykes, having innumerable backs,' or natural veins and fissures, interspersed through the mass, which facilitate its detachment from the parent rock; these rock masses exist to a depth practically limitless.

154. Opening New Quarries; Drainage; Gravitation.-In opening a new quarry the rock mass should be carefully examined with a view to taking advantage of the inclination of the bed joints, which, for economical quarrying, should dip towards the working face. The drainage of a quarry is also of great importance, and the floor level should, when practicable, be arranged so that the water can be drained from the working face by gravitation. The depth of the 'tirr' or overburden to be removed enters largely into the question of selection, and the amount of stripping necessary for a certain depth of rock face will in most cases determine the site of a quarry. When the overburden is deep, or forms a large proportion to the actual quantity of rock quarried, the cost of winning the stone will be correspondingly high. Gravitation, besides affording drainage facilities, assists to a considerable extent the process of quarrying and the removal of the material to the respective points at which it is to be treated, such as dressing-sheds and stone-breaking machines. By this means unnecessary handling is avoided, and economy promoted in carrying on the operations.

It is sometimes necessary, in order to secure the best quality of rock, as well as to limit the extent of the ground occupied, and also to economize stripping, for a quarry to be worked to a considerable depth below the natural surface. This at times may entail an expenditure for pumping water, in order to keep the floor of the quarry dry, while the lifting or

H

removal of the

uarried material by mechanical means in the form of cranes and aerial cableways becomes necessary.

155. Tirring or Stripping.-The tirring or stripping may be removed as necessity arises, or, as in the case where the quarries are worked under County Councils directly, it may be accomplished by the roadmen during frost when their services can be spared from the ordinary road work.

The earth removed should be deposited at a point not likely to interfere with the future working of the quarry. Attention to this matter will save a considerable amount of trouble and unnecessary expense in lifting it again at some other time. The overburden, when of a tenacious nature, or when it is frozen, may be advantageously broken up by sinking a few holes from 2 to 5 feet in depth, and charging them with some high-grade explosive; on this being exploded the ground will be sufficiently broken up to ensure its easy removal.

156. The simplest form of quarrying is that by which the material can be removed from the parent mass by picks, wedges, and levers. This is, however, only possible in certain quarries, which are by no means numerous, and recourse must usually be had to drilling and blasting.

157. Hand-drilling or Boring.-The boring or drilling of holes by manual labour, or, as it is termed, hand-drilling, is generally effected by either single or double-hand operations. The jumpers, or boring-tools, are for the most part now made from cast steel bars of octagonal section, supplanting those formerly in use made from round iron bars with steeled cutting edges. The cutting edge of the tool may vary in width from 1 to 4 inches, the stocks being of a somewhat less diameter, so as to enable the tool to free itself readily in the bore-hole; this also avoids the introduction of any unnecessary weight into the jumpers.

158. For instance, a boring-tool having a cutting edge of 1 inch in width is made from a steel bar gths of an inch in diameter, while inch bars are selected to make a boring-tool with 11-inch cutting edge, and so on in a similar proportion to tools or jumpers for boring a 2- or 3-inch hole, which are manufactured from bars of 15 inch in diameter. The cutting edge of the tool may be made straight or slightly curved for hand-boring; the straight cutting edge, although working more freely than those of the curved form, are somewhat weaker at the corners, and consequently liable to fracture.

159. Hand-drills and Jumpers.-The straight and curved cutting edges are shown in figs. 47 and 48, while fig. 49 represents a section of the chisel point, the sides of which should not form a greater angle than 70 degrees.

The steel bars from which boring-tools are made are generally cut into varying lengths as may be desired; the tools for boring holes of the smallest diameter are from 18 to 20 inches long, while those for boring holes of greater diameter may vary from 42 inches up to 6 or 7 feet in length. A blow given to a jumper is more effective the shorter the bar,

hence it is a common practice to make use of a number of tools, each succeeding one being somewhat longer, while at the same time the cutting edge is slightly reduced in width. The actual diameter of the hole drilled is somewhat greater than that of the drill-bit.

The striking face of the steel or stock should be flat, and in the larger sizes the diameter of the head is made less than that of the stock.

160. Hardening and Tempering Hand-drills.-The forging and hardening of boring or drill-bits are operations requiring much skill on the part

of the smith, so as to avoid the cutting edge and lower portion of the stock being burnt,' or the formation of water cracks'; and in tempering it is advisable, in order to obtain the best results, to let down the steel to a bright straw yellow.

161. Hammers and Sledges.-Hammers or sledges of cast steel are made of varying weights, according to whether the drilling is to be performed by the single-hand or the double-hand method. These vary considerably in shape according to the ideas and customs of the workmen in the different. localities where quarrying operations are carried on. The weight of hammers for single-hand boring is generally about 4 lbs., and as the expression implies, one man in a sitting position performs the whole operation by manipulating both tool and hammer. For double-hand drilling the sledge may be as heavy as 10 lbs., the shaft or helve, generally 30 inches long, being made of a wood having some elasticity, such as hickory, young oak, or acacia; ash is also much used for the shafts or handles of quarry tools. 162. Starting a Bore-hole. Single- or Double-hand Drilling.-The first step necessary in commencing drilling, after the tirring or stripping has been accomplished, is to fix the position of the bore-hole for blasting in the most advantageous manner, regard being had to the natural veins and fissures of the rock as a means of facilitating its detachment from the parent mass. It is necessary to remove any loose pieces of rock and prepare the surface by chipping, so that it may be nearly at right angles to the direction of the intended bore-hole. Double-hand drilling is sometimes performed by two men; one, sitting on the rock, guides and turns the jumper with one hand, and strikes, by means of a light hammer, alternate