NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXXIII, Issue 10079, 14 March 1896, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

LIFTING 111" .MAGNETISM.

"As interesting use of magnetism is being made at) the Sandycrofo foundry in England," gays Electricity, January 8. "At these works electric cranes are operated from the electric power and lighting circuits, together with electromagnets, which permit) the ready lifting of pieces of iron or steel weighing up to two tons. The magnets constructed tor lifting purposes arc attached to a crane. One magnet takes 5£ amperes at 110 volts to excite it, at which energy it will support a weight of two tons of iron or steal. A switch controls the supply of current delivered to the magnet. By the use of this magnet, or crano, three men do the work in one quarter of an hour Which previously took six men one hour and a-half to perform." ECLIPSE OP THE SDN.

The astronomical event of this year is the total eclipse of the sun, which will occur on 9th August next. The line of totality passos over Norway. In the neighbourhood of tho Varanger Fjord, to which the eclipse committee of tho British Astronomical Association has resolved to confine its attention, the duration of the eclipse on the central line will be just, two hours, and of totality 101) seconds. The sun will, in the locality selected, have an altitude of 15deg., or about that which it has at noonday in England in midwinter, With such an elevation a very satisfactory view of the eclip»o should be obtained, and the event is looked forward to with very groat interest in astronomical circles,

ELECTROPLATING A SHIP'S HULL, The Electrical World, November 20, sayslt is well known 'hat unless an ocean going vessel is plated with copper below its wator lino, barnacles and other animal and vegetable matter will accumulate on tho wetted surface and very considerably increase its resistance, thereby reducing tho speed of tho ship. Moreover, if the vessel be of iron or steel, a corrosive action takes place which shortens the life of tho hull. The above growths ofton extend to a thicknossof twoinohes or more, and on the large ocean-liners as much as 23 tons are not infrequently removed at one docking, and tiio cost of docking for this purpose and cleaning often exceeds £2500. The desirability of a method of coppering a vessel by which the copper can be applied directly to the steel shell, without the interposition of a wooden sheathing, is therefore evident. A solution of this problem is presented by a company which lias erected a plant) at Jersey City, and consists in an electrolytic method of depositing copper on the plates, which coating adheres so firmly as to mako its removal a most difficult matter; in fact, it is claimed lhat tho copper becomes practically a part of tho steel plate when tho process is complete. The copper is applied to the completed vessel and not to the separate plates, and hence existing vessels may take advantage ot this method to save dockage. Nor is the privilege confined to steel vessels alone ; for woodou vessels may be coppered by this method by first applying plumbago to their side-, To prepare the sides of a steel vessel for receiving its coat of copper, shallow baths are built, which are rectangular in shape and open on one side. Those baths are made water-tight by by moans of a coating of tar, and are provided on their edges with heavy eoftruboor gaskots. In the bottom of the bath are two pipes, through which the electrolyte is circulated. The bath is held up against the side of the vessel by polos. It is first filled with a pickling mixture composed of dilute sulphuric acid, and this remains in contact with the plate about twelve hours, after which it is removed and the plate scoured with sand and soda. If a sulphate bath should now be applied to this place a coating would be deposited, it is true, but duo to the free acid of tho mixture the coating would readily pool off. To avoid this, a preliminary coating is deposited, using a cyanide instead of sulphate of copper. About twelve hours sulßces to deposit this preliminary coating. Copper electrode; are placed in the bath and connected to tho positive torminal of the dynamos, which completely surrounds the boat and is insulated from it. The negative terminal of tho dynamo is firmly connected to the plating of the boat; itself. Tho sulphato bath is applied for forty-eight hours, and the coating allowod to reach a thickness of throe thirty-seconds to one eighth of an inch. The conditions are such that any number of baths may be applied to the vessel, and, therefore, the process is continuous, and tho actual time of plating does not make 80 much difference. The present method is to run two large mains around tho boat) to convey tho electrolyte, one a feeder, and the othor a return. Each bath taps on these mains from its two pipes, and a small steam pump pump* the sulphate of copper through the pipes and thence to a roservoir, only to bo pumped over again. Thus the baths ate kept continually agitated. At the forward end of tho boat a stand-pipe is erected, to maintain an approximately constant pressure to tho mains. At present work is being done on a small tugboat, tho plating of which is nearly completed. About fivo tons of copper will have been deposited when the work is completed. The plant consists of four dynamos of ten horse-power each,

MACIIINK V. INTiaUIIKNOK. Tho machine has run ahead ot tho human intelligence which operates it. A Western paper company, which has recently rebuilt a mill which was burned some months asjo, lias set up therein twoFourdrinier machines which, according to the contract ontered into by tho builder, are to run at the spoed of 400 feet per minute. One of them was •'tailed up recontly at a speed something less than that which the contract called tor. The machine worked all right, bub the attendants were nob accustomed to such fast running, and it embarrassed them. It became necessary to slowdown the machine in ordor to ailow tho tenders to get acquainted with it. The 400-foet-a----minute machine has como to stay. And it is only two years since unbelieving foreigners wore sure we woro drawing the long bow, when wo told them of machines in America that were running at the rate of 300 fcot a minute.

tub earth's rotation. The explanation of Lord Kelvin's estimate fchab the set-back" of the earth in its daily rotation round its axis amounts to twenty two seconds per century, is reported to be that such retardation is owing to the friction cause 1 by the tides, the latter acting as a brake, am I such action is calculated, according to the same authority, to be equal in weight to some 400,000 tons applied on the equator. Other causes, ho says, have also to be taken into account, as, for example, the increase in the size of the earth, duo to tho falling on ib of moteoric dust, which, if doposited at tho rate of one foot in 4000 years, would produco the observed retardation by itself. Further, such a phenomenon as tho annual growth and molting of snow and ice at the poles, by abstracting water from tho other parts of the ocoan, introduces irregularities into the problem, the abstraction accelerating the earth's motion, tho molting, by restoring the water, retarding it.

STOPPING MACHINERY. A contrivance for quickly stopping machinery— in case some parson is being drawn botween cogs or rollors—has boen devisod by a French electrician. On touching one of a series of push-buttons placed at convenient points, the power is shut off and a powerful brake is applied to fly-wheels. A twenty horse-power engine, working ab ninety revolutions, was stopped in two-thirds of a second.

A FRENCH SUBMARINE BOAT. L' Energio Eleotrique, December 1, contains an illustrated description of the submarine boat Goubet which has just bean completed, and with which experiments were made in Paris. A brief description is given as follows" lb id shaped somewhat like a cigar but is pointed equally at both endi; it is 26 feet long, about 12 feet in width, and is made of gun-metal. Access to it is made by means of a manhole at the top, and which can be hermetically sealed ; the weight is 10 tons, and it is calculated to resist tho water-pressure ab a depth of 160 fathoms. There is room i.n it for one officer and one or two sailors; the air is stored in stool cylinders, uAder pressure, and the vitiated air is exhausted by means of pumps; to make it si(,ik water is admitted to chambers provided for that purpose. Tho motor power is a battery of 56 cells of accumulators, weighiug about 1 ton, and giving 20 ampores at 90 volts for 14 hours; tho propeller makes 250 revolutions, and the steering is done by altering the direction of the screws ; in case of accident a weight carried all tho bottom can be detached, and tho boat thou immediately rises .to ifcho Bw/aw.'l .