for the performance of long and perilous voyages; and it was a bold conception which suggested that they should be sent round the Cape, to the eastward, in the very worst season of the year, when even the stoutest and largest wooden ships trust themselves as little as possible in that stormy region.
The equipment and destination of the Nemesis, however, was kept a profound secret, except to those who were personally concerned in it, and even they (with the exception of the authorities) had little notion of the precise service upon which she was to be employed.
The Nemesis was at length finished, and sent to sea as a private armed steamer. She was never commissioned under the articles of war, although commanded principally by officers belonging to the Royal Navy; neither was she classed among the ships of the regular navy of the East India Company. In short, the Nemesis was equipped under very peculiar circumstances, which, together with the novelty of her construction, caused her to become an object of very general interest. The "wooden walls" of England had, in fact, been so long identified with her proudest recollections, and had constituted for so many centuries her national "boast," that it seemed an almost unnational innovation to attempt to build them of iron. Indeed, it was rather looked upon as one of the dangerous experiments of modern days. Moreover, as the floating property of wood, without reference to its shape or fashion, rendered it the most natural material for the construction of ships, so did the sinking property of iron make it appear, at first sight, very ill adapted for a similar purpose. It was sometimes forgotten that even wooden ships are composed of wood, iron, and copper together, and that the bulkiness of these necessary materials greatly diminishes the buoyancy of the wood.
A minute and scientific description of the structure of the Nemesis will be found in the United Service Journal for May, 1840, and it will therefore be sufficient, in this place, merely to notice one or two peculiarities, in which it differs from that of wooden ships in general. With the exception of the great paddle-beams, across the ship, and the planks of the deck and the cabin-fittings, together with one or two other parts, the names of which would be only intelligible to the scientific reader, the whole vessel was built of iron.
Credit is due to Mr. Laird, of the Birkenhead Iron Works, Liverpool, for the admirable manner in which she was constructed, and for the elegance of her form and model, which fully answered every purpose required of her.
Her burden was about 680 tons, and her engines of 120-horse power, constructed by Messrs. Forrester and Co., also of Liverpool; and with twelve days' supply of coals, together with water and provisions for four months, and stores of all sorts for two years, with duplicate machinery, &c., and all her armament complete, her mean load draught of water was only six feet. But commonly, in actual service, she drew little more than five feet. Her length over all was 184 feet, her breadth 29 feet, and her depth 11 feet. Her keel-plate was laid, and the vessel built and launched, in the short space of three months.
Strictly speaking, the Nemesis has no fixed keel, but the lower plate of iron, which connects the two sides of the ship together along its middle, is called the keel-plate. She is, therefore, almost perfectly flat-bottomed; and, in order to obviate, as much as possible, the disadvantages attendant upon this peculiar construction, there are two sliding or moveable keels, capable of being raised or lowered to the depth of five feet below the bottom of the vessel. Each of these keels is about seven feet in length, one being placed before and the other abaft the engine-room. They are each enclosed in a narrow case or tank, one foot wide, running from the bottom of the vessel up to the deck, and which, of course being open below, allows the water to rise in it, to the level of the sea on the outside of the vessel. In this, the keel, which is of wood, 4½ inches thick, works up and down by means of a small winch, and a strong chain which is attached to it. Thus it is evident, that either the foremost or the aftermost keel can be raised or lowered, independently of the other, if circumstances require it.
As it would, however, be impossible to steer with accuracy, a vessel of this construction, with a rudder merely of the ordinary description, and which, from its shallowness, would, in a heavy sea, be in a great measure out of water, there is a contrivance by which a moveable or false rudder is attached to the lower part of the true or fixed rudder, and which descends to the same depth as the two false keels, and, like them, can be raised or lowered at pleasure.
The main or true rudder was composed of wood, but the lower or false rudder was made of iron, and was so constructed as to grasp the lower part of the upper or fixed one, firmly on either side, but was bolted through in such a way as to be moveable, as if it were fastened by a hinge, so that, by means of a chain run up to the taffrail from its outer edge, it could be hauled up to any height required.
The next striking peculiarity in the construction of the Nemesis was, that the entire vessel was divided into seven water-tight compartments, by means of iron bulkheads; so that, in fact, it somewhat resembled a number of iron tanks, cased over, so as to assume the external form of one connected vessel. By this means, the occurrence of any accident, such as striking on a rock, or shot-holes, &c., which might occasion a dangerous leak in one compartment, would have no effect upon any other part of the vessel.
The advantages of this arrangement were often tested, during her three years' hard service; and, indeed, within a few days after her first departure from Liverpool, as will be presently related, this contrivance sufficed to save her from the almost certain destruction which would otherwise have awaited her.
The last peculiarity which it seems necessary here to mention, was the provision of some kind of instrument for counteracting the effect of the local attraction of so large a mass of iron upon the compasses, and for correcting the errors occasioned thereby. This difficulty had been seriously felt by Colonel Chesney, on board the small iron steamers which he had under his orders, during his expedition to the Euphrates; although he was of opinion, that the placing of the compasses at a certain height above the vessel, so as to be further removed from the sphere of the local attraction of the iron, was sufficient to reduce their errors materially.
Without entering into the merits of Barlow's counteracting plates, or Professor Airy's interesting discoveries, it will be sufficient here to mention, that the Nemesis was fitted with correctors, very much according to the system of Professor Airy, but not under his own superintendence; that the experiments were conducted at Liverpool under every disadvantage, and that the result was never perfectly satisfactory. Indeed, the accident which shortly befel her, has been attributed, upon strong grounds, principally to the imperfection of her compasses. It is right, however, to mention, that other vessels, such as the Phlegethon and Pluto, which have been fitted with Airy's correctors, tested according to the most approved principles, and after experiments conducted with great attention, have been totally relieved from this source of danger and anxiety, and have been navigated with perfect accuracy and confidence.
We may now come to the interesting moment of the departure of the Nemesis from Liverpool, where she was built. Everything seemed at first to prosper; the weather was favourable, and the machinery perfect in all its parts. She had cleared the narrowest part of the Irish Channel, had passed the coast of Wales, and crossed the entrance to the Bristol Channel; and the course she had been steering would have taken her well clear of the Land's End.
It was now the second day since her departure. About two o'clock in the morning, the weather being still hazy and the night dark, she struck heavily on a rock.
Of course the engines were instantly stopped, but the way she already had on her appeared sufficient to carry her over the reef; and, indeed, the actual rocks themselves could be seen outside of her, so that she had evidently passed between them and the land, and had merely struck the edge of the reef.
Finding that the vessel did not hang upon the reef, and was therefore still afloat, her head was turned to seaward, and the engines kept working slowly, while the dawn was anxiously expected. It was now discovered, that the rocks upon which she had struck were aptly enough called "The Stones," lying at the entrance to the bay of St. Ives, in Cornwall,
