In the steam hammer (fig. 4), which was first patented by Nasmyth in the year 1842, this objection is completely obviated. By the simple device of attaching the hammer head to the lower end of the rod of a piston working in an inverted steam cylinder, he produced a machine eap- able of being made to deliver its blows with a foree to which no limit has yet been found, and yet so perfectly under control as to be able to crack a hazel nut without injuring the kernel, To the introduction of this invalu- able tool is due more than to any other single cause the power which we now possess of producing the forgings in iron and steel which are demanded by the arts of modern times ; and in one or other of its many forms it is now to be met with in every workshop in which heavy work is carried on, Many modifications of the Nasmyth steam hammer have been introduced. In one of these steam pressure has been applied above the piston to intensify the blow, it being only used in the original form for lifting the “tup” and piston and for regulating their descent. In another the piston and piston-rod have been attached to the framing, and the cylinder made movable, its weight being thus added to that of the hammer.
Duplex hammers differ materially fren the ordinary steam hammer, inasmuch as no anvil is necessary,—two hammer heads of equal weight (and for some purposes they weigh only a few pounds, for others as much as 30 tuns) being made to deliver horizontal blows of equal force simultaneously on opposite sides of the forging, which thus receive perfectly equal treatment. The importance of this may be gathered from the fact that every increase in the weight of the vertical steam hammer necessitates a very much larger increase in the weight and solidity of the anvil which is necessary to afford the requisite inertia for resist- ing the blow. For instance, the anvil of a 40-ton hammer now in use at Woolwich Arsenal weighs upwards of 160 tons, and bas nearly 500 tons of iron in its foundation, whereas the anvil of an 80-ton hammer of which a full- sized model was amongst the most striking objects at the Paris Exhibition of 1878, is of no less than 720 tens weight.
The recent growth of steam hammers to the enormous size just mentioned is due chiefly to the large dimensions, independently of the mere weight, of the forgings which have now to be made for heavy ordnance and for other purposes. As Jong as the thickness of a forging is moder- ate, the reaction of the anvil acting upon its under side has an effect not greatly inferior to that of the hammer on the upper side, But with every increase in thickness some of this reaction is lost and the effect of the blow is more and more confined to the outer portions of the mass, which thus receive more than their share of treatment at the expense of the central portions. On this account the difficulty of obtaining thick forgings thoroughly sound throughout their substance is very great, and it seems as if we had now reaghed the limit beyond which the hammer cannot be advantageously applied for their production, It has been found indeed in the case of large shafts that dispens- ing altogether with the central portion, thus making them tubular instead of solid, is accompanied by an increase in their strength, owing to the possibility of thus forging the metal uniformly throughout. Bat a much more widely applicable remedy, and one which will doubtless come into general use for heavy work, is the substitution of hydraulic or other pressure for the force of impact, a system which has lately been employed by Sir Joseph Whitworth with wonderfully good results. The renson of the superiority of its effect seoms to be mainly this, that a certain amount of time is essential for completing the “flow” of the metal which it is the object of forging to induce. Under continuous pressure this flow can take place uniformly throughout the mass, whereas the instantaneous blow of the hammer, though it acts violently on the surface particles, and to a decreasing extent on the adjacent ones, is entirely expended before the action has had time to reach those at the centre, so that unequal density and consequent weak- ness is the result. For massive forgings therefore the old saying can be no longer accepted that * there is. no machine like a hammer.”
HAMMERFEST, the most northern town in Europe, is situated in the department of Hammerfest in the province of Finmark, on the western side of the island of Kvali (ie, “Whale Island”), which lies off the north-western. coast of Norway. Its latitude is 70° 39’ 15”, and the sun stays for two months above its horizon. Though a small place of about 2100 inhabitants, it is the scat of a considerable trade, in which not only Norwegian and Danish but English, German, and particularly Russian vessels are engaged. About thirty small ships are sent out from Hammerfest every spring to Spitzbergen to tke part in the fisheries and walrus hunting. Train oil from the liver of the Scymnus microcephalus aud cod-liver oil are manufactured in the town. The exports, among which salted fish occupies the principal place, amounted in 1876 to the value of 1,629,500 crowns (£90,528), and the im- ports, chiefly salt and coal, to 721,700 (£40,094). On the Fuglenaes or Birds’ Cape, which protects the Larbour on the north, there stands a column with an inscription in Norse and Latin, stating that Hammerfest was one of the stations of the expedition for the measurement of the arc of the meridian, Nor is this its only association with science ; for it was one of the spots chosen by Captain Sabine for his series of pendulum experiments. The ascent of the Tyven or Diebsberg in the neighbourhood ig usually undertaken by travellers.
HAMMER-HEAD. See Shark.
