Size of sails.
Besides the mizen-mast, which is of wood, there are five other masts of hollow wrought iron. Two of these carry large square sails, the others fore and aft sails, the fore-mast having a jib as well as trysail, there being neither bowsprit nor jibboom. The standing rigging consists of iron wire rope, and the lower mast shrouds of this material are 8½ inches in circumference. The running gear, manufactured chiefly from Manilla hemp, is beautifully made. Instead of the ordinary dead-eyes and lanyards, an ingenious contrivance has been devised for letting go the shrouds instantaneously on an emergency. When under full sail the Great Eastern will spread 6500 square yards of canvas.
Magnetic apparatus of Mr. J. Gray.
The magnetic apparatus or floating compass invented and patented by Mr. John Gray, of Liverpool, is to the navigator, perhaps not the least interesting instrument of the great ship. The binnacle consists of an isolated battery of magnets adjusted by vertical screws, which move them in proportion to the deviation of the compass arising from the influence of the iron used in the construction or equipment of the ship. The original error having been ascertained by careful observations (a duty invariably devolving on the makers of the instrument) and the compass thus adjusted and regulated, the process of readjustment, when necessary, is so simple that, by the officer of the ship merely placing her head in two positions—north and south, east and west—the compass in the northern hemisphere can be made perfect. If any alteration takes place in the ship’s magnetism of an opposite character in the southern hemisphere, by reversing the position of the magnet and by adopting the same process, the instruments will be found as correct as in the northern. There are other applications all calculated with the utmost precision for navigating the ship, one of which is highly important, in that it corrects the dangerous influence arising from heeling. A vertical magnet is made moveable in the centre of the apparatus so as to obviate errors arising from this cause,—errors sometimes amounting, by the deflection of the needle, to 50 or even a greater number of degrees. As these disturbances produce considerable oscillating of the card when the vessel rolls, their repetition often causes a momentum that ultimately makes the card revolve with such velocity as to render it useless to the helmsman.
The patent floating compass, constructed to prevent vibration from affecting the centres of action, consists of an inner bowl floating in an outer one, the object being to render the former insulated in its water bed, the exterior being solely influenced by the action of the ship. Through a very ingenious mechanical arrangement in the interior of the inner bowl the hardest gems and the finest centres may be applied without fear of oscillation of the card. The entire combination of these essential points insures steadiness of action, perfect indication, and great durability.
There is also a vertical double disk to register the ship’s course and to show whether the man at the helm has attended strictly to his instructions with regard to the course to be steered. On each side of the binnacle there is a metal box containing soft iron for the adjustment of any small amount of deviation in the quadrants, which remains stationary with its contents throughout every change of latitude.
Apparatus for steering.
Nor must I omit notice of the mode of directing the course of the ship. On one side of the platform between the casements of the paddle-wheels (the deck most in use by the commander and officers of all steam-ships), stands an ingenious apparatus, in which there is a compass, the duplicate of the one in the binnacle, and before it an officer stands when the ship is under weigh, who is under the immediate eye of the captain. This pedestal is covered with a brass circular slide, with an aperture sufficiently large to permit of one of the points on the card being seen through it. The captain or officer in charge of the ship, by turning a handle, exposes the point at which he wishes the ship’s head to be kept, and by means of connecting rods a coincident point is disclosed on the compass in the binnacle, which is watched by the steersman, who thus knows in a moment the course he has to steer, so that, without verbal orders (which are frequently indistinctly heard and sometimes misunderstood, even when the officer is close to the helm) the ship is directed on her course with more ease than an ordinary sized vessel.
Beyond the original plan contemplated of manufacturing gas on board to be laid on to all parts of the ship, it was further intended to carry the electric light so as to secure a perpetual artificial moonlight around the vessel.
Rudder and anchors.