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 ARMSTRON G 673 into the plate before explosion takes place, the effect is impact, and metal becomes heaped up and heated, and small. Consequently only those shells whose calibre cracking may take place many minutes after impact. In considerably exceeds the thickness of the armour attacked Fig. 7 may be noticed round each point of impact a concan be used with good effect, and the preponderance should centric circle of lighter shade than the rest of the plate, be greater with high explosives than with powder. In which extends gradually, and has been likened to the consequence of the destructive effect of shells charged with swelling of a black eye. Badly-made plates have been melinite and other high explosives on stone or earthworks, known to break spontaneously, and steel shot have done armoured structures have been adopted for inland defences the same. Compound armour was made by running on the Continent. These generally take the forms of molten steel on to a white hot foundation plate of rolled cupolas and shielded mountings, which may be fixed, wrought iron on Wilson’s process, or by attaching a thin disappearing, or even portable. Fig. 10 shows a disappear- steel face plate to a wrought-iron foundation by running ing shielded mounting. The gun is protected by a steel molten steel in between them on Ellis’s process. In the armoured curved roof A, fixed on a central pillar Bd and Harvey process the face is carbonized by contact with DE, on which the whole system revolves. The gun is carbon at a high temperature, kept up for several days, the shown in action, the weight being held up by a counter- face being finally water-hardened. There is some difficulty weight G at the end of a lever Fh. The gun can be run in bringing such plates to the exact curve required for the back inside the port, and the roof lowered to rest flush ship’s side, because face hardening causes contortion. It with the “glacis plate” or “vorpanser” CH. When is possible to flatten a plate slightly by compressing the thus taken out of action the gun is hardly open to attack hard face, but not to bend it further by stretching it. of any kind. Until recently, armour under 5 inches thick could not be With regard to manufacture, the newest and most inter- Harveyed, because contortion could not be controlled. In esting processes depend on delicate methods of treatment, the Krupp process carbonization may be produced by the which are carefully kept secret, so that information of a action of gas, but not necessarily so. Some of the stages general character only can be given. Wrought iron is of manufacture require much experience, so that great formed from scrap worked into slabs, and piled and rolled expense and waste of material are apt to be involved in in so many successive processes that an 8-inch plate was first adopting the process, especially with thick plates. It said to have been rolled out of a column nearly 100 is said that in this process metal is at times used which feet high. Specially soft fibrous iron was used. It was would be expected to prove brittle, but which, after being considered not only that great' power of drawing out, but subjected to treatment that would be likely to render it of doing so easily was necessary, because some metal, which still worse, is eventually made very tough. Up to the might draw out well slowly, might tear in preference under present it has probably owed some of its qualities to the a blow. Steel has been used of all descriptions, from presence of nickel. It has been said that nickel would be something closely resembling wrought iron to really hard dispensed with, but such reports have hitherto been contrametal. Molecular displacement occurs round the point of dicted. (c. o.-B.)

Armstrong1, William George Armstrong, Baron (1810-1900), British inventor and founder of the Elswick manufacturing works, was born on 26 th November 1810, at Newcastle-on-Tyne, and was educated at a school in Bishop Auckland. The profession which he adopted was that of a solicitor, and for a number of years he -was engaged in active practice in Newcastle as a member of the firm of Donkin, Stable, & Armstrong. His sympathies, however, were always with mechanical and scientific pursuits, and several of his inventions date from a time anterior to his final abandonment of the law. In 1840 he published a paper on the electricity of effluent steam. This subject he was led to study by the experience of a colliery engineman, who noticed that he received a sharp shock on exposing one hand to a jet of steam issuing from a boiler with which his other hand was in contact, and the inquiry was followed by the invention of the “ hydro-electric ” machine, a powerful generator of electricity, which was thought worthy of careful investigation by Faraday. The question of the utilization of water-power had engaged his attention even earlier, and in 1838 he made his first contribution to hydraulic engineering by inventing a rotary water motor. Soon afterwards he designed a hydraulic crane, which contained the germ of all the hydraulic machinery for which he and Elswick were subsequently to become famous. This machine depended simply on the pressure of water acting directly in a cylinder on a piston, which was connected with suitable multiplying gear. In the first example, which was erected on the quay at Newcastle in 1846, the necessary pressure was obtained from the ordinary water mains of the town; but the merits and advan-

tages of the device soon became widely appreciated, and a demand arose for the erection of cranes in positions where the pressure afforded by the mains was insufficient. Of course pressure could always be obtained by the aid of special reservoirs, but to build these was not always desirable, or even practicable. The first way in which Armstrong attempted to meet the difficulty was by the use of an air vessel, but this did not prove very satisfactory in the few cases in which it was tried. Hence, when in 1850 a hydraulic installation was required for a new ferry station at New Holland, on the Humber estuary, the absence of water mains of any kind, coupled with the prohibitive cost of a special reservoir owing to the character of the soil, impelled him to invent a fresh piece of apparatus, the “ accumulator,” which consists of a large cylinder containing a piston that can be loaded to give any desired pressure, the water being pumped in below it by a steam-engine or other prime mover. This simple device may be looked upon as the crown of the hydraulic system, since by its various modifications the installation of hydraulic power became possible in almost any situation. In particular, it was rendered practicable on board ship, and its application to the manipulation of heavy naval guns and other purposes on warships was not the least important of Armstrong’s achievements. The Elswick works were originally founded for the manufacture of this hydraulic machinery, but it was not long before they became the birthplace of a revolution in gunmaking; indeed, could nothing more be placed to Armstrong’s credit than their establishment, his name would still be worthy of remembrance, for they have contributed enormously to the progress of the world in the S. I. — 85