cement at the gables and wall plates, as shown in fig. 96. Ventilators of a zigzag form should be constructed in the walls below the level of the flooring, immediately above it, and also at

the roof of the store, a free circulation of air being desirable to keep the explosives in good order, while at the same time it aids in preserving the woodwork in the interior of the building. These should be protected on the outside with cast-iron perforated plates or bricks, and on the inside with wire cloth. The exterior of the building should be covered with a coating of cement, to ensure its being perfectly waterproof.

Double doors of wood are sometimes provided, but a door-frame of

wood lined on the inside is quite sufficient. To properly protect it from being tampered with, a sheet of iron of an inch thick should be spiked on

to the outside of frame, so as to slightly overlap both it and the recess, which is formed of angle irons, as shown in the drawings. The side at which the

M

door is hung should have the brickwork 14 inches thick, while the arms forming the hinges should be fixed by through bolts and iron plates inside. The flooring must be of timber, the interior of the store must be lined with wood, and these along with the shelving must be fastened with copper, brass, or zinc nails, or with irou nails countersunk and puttied. The woodwork

should be finished by applying two or more coats of varnish. The lock should be of brass, and all iron, where exposed internally, properly protected. It is essential to provide a lightning-conductor, which may be made of -inch round iron, or of copper tape inch by inch, properly fixed to the outside wall (as shown), and terminating in the earth preferably (damp soil),

2 or 3 yards distant from the store, and 3 feet deep with a copper plate 20 inches by 12 inches and of an inch thick. All exterior ironwork should be put in metallic connection with the conductor, the upper end of which should be 18 inches above the highest part of the building, and terminate with three branches pointed; these should be gilded or finished with

platinum caps to resist oxidation. It is necessary to keep the floor and shelving of the store free from grit, for which purpose they should be swept periodically, and occasionally washed.

Wallplate 92"

232. Annexe for storing Detonators.-The detonator 'annexe' is best formed by a box made of iron -inch thick, 2 feet by 2 feet and 2 feet 6 inches deep, sunk three-fourth parts into the ground. The lid should project 1 inch over the box, and be slightly bent downwards at the outer edges to prevent wet gaining access. The lid should be provided with strong hinges and brass padlock. The interior of the box should be lined with wood, and have a suitable inner lid or cover. This annexe may be placed as shown in fig. 93, just clear of the wall of the explosives store. An additional safeguard in the form of a high and close fence may be erected a few feet distant from the store, completely surrounding it, and having a suitable access in front. It is necessary to provide a pair of boots without steel or iron about them, or a pair of goloshes, to be used by those entering the store. These should be of a size large enough to wear over the ordinary boots or shoes. As a convenient road to the store is a necessity, the site selected for the store will mainly depend on the facilities for making and properly maintaining such a road.

Lining

FIG. 96.-Timber roof for store with
galvanized covering.

233. Cost of Erection.-The cost (exclusive of the road access) of erecting an explosives store of the dimensions given in the drawings will vary according to the place in which it is erected; but the expenditure may be taken at from £20 to £25, if the brick arch is adopted, and about £16 to £20 when the roof is formed of timber and galvanized corrugated iron, as shown in fig. 96.

234. An excerpt from the Explosives Act should be affixed on the outside fence; and the rules and regulations should also be hung up inside the store, while the class of the Division should be painted on the outside of the door in large letters in the following manner :

DIVISION D. 4000 lbs.

CHAPTER VI.

STONE BREAKING AND HAULAGE.

Stone Breaking.

235. The material described in the preceding chapter requires a further reduction in size before it can be applied to the highways or stored for subsequent use.

236. General Conditions relative to Hand-broken macadam.-If the macadam is for coating the top of a newly constructed road, or for strengthening an existing one the crust of which has, through neglect or other causes, become reduced to such an extent that the material forming the bottoming is exposed, then it is necessary to apply metalling, the stones of which will pass through a 24-inch ring, or weigh about 6 ounces. For general surface repairs, however, metalling of a somewhat less size may be advantageously made use of. The smaller the size the smoother will the surface of the road be; but the size of the metal for any particular section of a road must be determined to a certain extent by the amount of traffic which it will have to bear, and the nature of the rock from which the macadam is produced.

On roads over which the traffic is heavy, the tougher kinds of rock, such as basalt and syenite, should be of a size which will pass through a 24-inch ring; while with the same class of material, but applied on a road with only moderate traffic, the size may be advantageously reduced to pass through a ring 2 inches in diameter. The weights of these different sizes are approximately 4 ounces and 3 ounces respectively. Rock of a hard siliceous nature will give better wearing results when broken to a size somewhat larger, while flints and the harder limestones will be most suitable for surface repairs if broken to a size the weight of which varies from 6 to 8 ounces.

To ensure equal wearing, and consequently a smooth surface, the metal should be broken to a uniform size and to a form as nearly cuboidal as pos-sible. An irregularly-sized metal cannot resist the wear and crushing effect caused by the wheels of passing traffic; consequently a bumpy surface is formed, or, in other words, it becomes 'cupped.' Under these circumstances the wear is increased, and the surface of the road becomes irregular, and horses and vehicles suffer in proportion.

237. These are briefly the main points necessary to be considered in determining the best conditions under which hand-broken metal is applicable to road repairs, especially when the material is intended to be consolidated by wheel traffic. The breaking of metal specially to a small size for ordinary repairs, although of great advantage to the road under certain conditions, increases the cost of production, and in most cases a proportionately larger amount of small stuff is produced. This fine material is of little or no value on the road, and under certain conditions its presence is pernicious; to avoid this evil it is necessary to screen the material so as to separate it from the regular-sized stones. This additional manual labour increases the cost of production, which, at a low estimate, may be taken at 3d to 4d. per cubic yard.

238. Quantity of macadam broken by Hand per Day.-A good handbreaker can produce from 3 to 4 cubic yards of ordinary macadam per day out of such material as flints, the harder limestones, field stones, and river gravel. Whinstone of a siliceous nature, when the rock is reduced to a size similar to that mentioned in the preceding chapter on quarrying, may be broken by hand at the rate of 2 to 2 cubic yards per day, while syenite, basalt, and the tougher kinds of whinstone can be broken up at the rate of from one-half to one cubic yard in a similar time. The number of hours which a man works when breaking road metal depends upon circumstances. If engaged on piece work a hand-breaker may work for twelve hours on a stretch, producing more material than one who is less physically capable, or who is engaged to break at so much per day.

239. Cost of Hand-breaking.—It is thus a somewhat difficult matter to arrive at the actual cost of breaking road-metal by hand, but an approximation sufficiently correct can be obtained by measuring a heap of metal which has occupied a hand-breaker a certain time to accomplish. This will give the amount broken each day of nine or ten hours; but, in addition to this, the wages which are paid in any particular locality will have to be considered as influencing the cost of production. Taking these circumstances into consideration, the experience of the author is that the cost of breaking by hand. varies from 1s. 3d. to 2s. 6d. for each cubic yard of road metal. The supplying of macadam for repairing and maintaining roads under the old, or patching system, is in most cases regulated by annual contracts. The price in some instances is stated separately for quarrying, carting, and breaking; but generally these contracts are arranged for at an inclusive figure, the metalling being deposited alongside the roads at convenient points or in depôts.

The price per cubic yard of metal thus laid down will vary according to the conditions already mentioned, and, in addition, the cost of hauling or conveying it from the quarry to the roadside depôts, especially where the distance is great, may increase the price to double the actual amount of producing the macadam itself.