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extensive tests have been made with pipes constructed on this plan, and it has been found that the plates have always given way before the joints, even where the plates have stood an enormous hydraulic pressure before parting. For connecting the pipes the old style of flange-joint has been dispensed with, its place being taken by a wrought-steel thimble or ring (Fig. 4). This is made wide enough to take a good bearing on each pipe, and has a packing of molten lead run in between the pipe and the tapered inner face of the thimble. Thus a wedge or dovetail joint is formed which prevents the egress of water, and this combination of thimble coupling and lead packing has been found to answer its purpose admirably. A practical mind will at once grasp many of the advantage? which are peculiar to this class of pipe as compared with the ordinary style of riveted pipe— e.g., no necessity for caulking ; reduction of friction consequent on smooth inside surface; great lengths attainable with corresponding reduction of pipe-joints ; increased strength and stiffness which greatly reduces the tendency to sag when pipes are carried on trestles. Each pipe is thoroughly coated with asphaltum, both inside and out. The Government of South Australia has already put this class of pipe to actual test and use, and, after very careful inquiry, it has been adopted by the Government of Western Australia for the Coolgardie goldfields water-supply scheme, the pipes being 30 in. in diameter, and having a united length of about 330 miles. For mining purposes the invention should make its way, as this pipe is applicable for the transmission of compressed air as well as water.

A SIMPLE MINE-VENTILATING FAN. Some years ago, when holding the position of manager of extensive collieries in the North of England, circumstances made it necessary for me to devote some practical attention to the design of centrifugal ventilators for mining purposes, the result being the double-inlet fan bearing my name, which has been in actual use for the last ten or twelve years, with satisfactory results. The objects attained are the complete absence of vibration so common to fans of the Guibal type, and the reduction of size and consequently weight, both in the machine itself and in its foundations and masonry, as compared with Guibal and other large fans. By making these fans of moderate diameter, they may be driven at a greater number of revolutions per minute than the fans alluded to, yet are not open to the objection which some mining-people raise to the very large number of revolutions per minute at which fans of small diameter have to be driven in order to attain the required circumferential velocity. My fans may thus be said to occupy a position midway between the two extremes, combining, as far as possible, the advantages, and in like manner eliminating the disadvantages, of both. As it appears more than probable that a system of mechanical ventilation will have to be introduced at some quartz-mines, and even now is desirable at some of the smaller collieries, as well as others of medium extent, in the colony, I have given further thought to the subject, in the direction of designing a fan which, whilst retaining those features so essential in a really good mine ventilator —viz., freedom from vibration and a capacity for yielding a satisfactory percentage of useful effect —shall be so simple that the bulk of its construction and its erection may be effected by the mine blacksmith and carpenter at comparatively little cost. Such a ventilator is illustrated. The air is taken in at one side only, and discharged freely all round the circumference. It may therefore be classed as a " single-inlet, open-running fan." The blades are gradually tapered from the circumference of the inlet to their tips, in order to maintain uniform area, thereby preventing a backrush of air info the fan, which would inevitably be the case if the blades were parallel or nearly so. When the air leaves the tips of the blades its velocity is considerable, but, as it is most desirable that this velocity should be reduced as far as possible before the discharged air meets the outside atmosphere, I provide expanding outlet-cheeks b, b, as a continuation of the contracting cheeks B, B, between which the blades revolve. Many fans are made with parallel blades enclosed by a drum-like casing, having an outlet in the form of an expanding chimney. Near the base of the chimney an adjustable shutter is fitted for the purpose of regulating the area available for the discharged air, and so preventing a backrush ; but, as the air is hurled against this shutter very abruptly, and the position of the shutter frequently incorrect, the device is not by any means an unqualified success. A much better arrangement is Walker's patent V shutter, which contracts the area in a gradual manner, and conducts the air into the chimney, where its velocity is materially reduced before finally escaping into the atmosphere. It is, however, infinitely better to correctly taper the blades so as to entirely obviate the possibility of back-rush than to build a fan with parallel blades and then have to add extraneous appliances to counteract the undesirable effects which such a fan is inevitably bound to produce. Having briefly given some idea as to why the blades are tapered, I may now state that in building one of the simple fans illustrated the following parts should be procured from an engineer-ing-works : (1.) The shaft. This may be of tough rolled steel. (2.) The plummer-blocks. These should have a bearing length equal to two and a half times the diameter of the shaft, and be provided with oil-feeders of large capacity. (3.) The two sets of arms, formed of T-iron or light tram-way-rails bent to the required backward curve (see drawing), with holes drilled or punched for rivets securing the blades, and bosses cast on in the centre. (4.) The belt-pulley, the width of which should not be less than five-eighths of its diameter. Having these parts, the rest of the work is easy.