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of the mould. Holding this tightly in the left hand, it will be easy to blacklead and polish the edge as well as the front without encroaching too far up the sides. When this has been satisfactorily effected, the paper strip, which served as a guard, can be removed. Now, taking a piece of the No. 18 or No. 20 bare copper, and gripping one end in the vice, he will wind it two or three times round the blackleaded edge of the work, so as to grip it firmly and make good electrical contact with the black lead under it. The extremities of this wire are brought together and twisted tightly, so that the coils may not loosen. The wire should now be cut off at a distance of about 10
in. from the work, and bent upwards at right angles to the front of the mould. An anode is now selected, having a diameter as nearly as possible that of the front of the mould. (This wire, so far as it will be immersed in the copper sulphate solution, must be painted over with a little Brunswick black, otherwise it will be eaten through by the solution.) The other end of this wire must then be clamped under the terminal affixed to the carbon (or positive) pole of the dry cell, and then bent twice at right angles in such a manner that the anode can lie flat at the bottom of the dish, which must be placed near the dry cell. The dish should now be filled to a height of about 1 to V/\ in. from the bottom, with the copper sulphate solution prepared as directed. The work to be copied is now- attached, by its slinging wire, to the zinc (or negative) pole of the dry cell, and the wire
so bent that the front of the mould is immersed in the solution as far as the wire binding extends, or, say, for a depth of about J4 hi. The work should lie perfectly horizontal, facing, but not touching, the anode, at a distance of about 24 in- to 1 in. from its surface. In immersing the mould, care must be taken to avoid air bubbles, and this can be done by letting down the front of the mould, somewhat tilted, so as to allow any air bubbles to escape; the wire can afterwards be straightened to cause it to lie horizontally. Great care must be taken that good metallic contact is made between the two wires and their respective dry-cell terminals; and also that no chance contact occurs, either between these two wires on the one hand, or between the mould and the anode on the other. After thus connecting up, the front of the mould should be allowed to remain in the solution for about fifteen minutes. It should then be examined in order to judge of the success of the work.
If the binding wire shows that it has received a rosy-pink deposit, beginning to extend to the edge and creeping round to the front of the mould, all is going well—the current is of the right strength; and if the mould be carefully replaced in the solution, the terminal contacts being maintained tight and good, it will be found that after ten or twelve hours' immersion the entire surface of the mould will have received a delicate coating of copper. To get a layer i-ifi in. thick it may be needful to continue the operation for three or even four days, or even to replace the dry cell by a fresh one, according to the size of the mould. Cut if, on examination, it is found that the surface of the binding wire and of the front of the mould are coated with a ruddy brownish mud, tending to fall to the bottom of the dish, and especially if bubbles of gas form on and round about the mould, it is a sign that the current is too strong. In this case it will be necessary to remove the anode farther away from the front of the work, or even to insert a "resistance" in the shape of a foot or two of No. 36 iron wire between the anode and the carbon terminal of the dry cell. When it is considered that the copper deposited has attained sufficient thickness, the mould should be removed from the sulphate of copper solution, the wire detached from the dry cell, and the mould washed for some time in a stream of running water; after which it should be slung up by its wire to dry thoroughly in a warm place. When the work is quite dry, the binding wire is untwisted, and the wire carefully unwound from round the edge of the work. If the copper deposit is very thick at these points it will be advisable to file it down cautiously all round, so as to avoid breaking away any of the copper deposited on the front. Having thus filed away any copper that may have extended round the edges of the work, the front of the mould should be held for a few seconds before a clear fire so as to warm the copper coating. This will cause it to expand slightly, after which, by cautiously pushing with the fingers from the back of the mould, the copper coating or "electrotype" can easily be detached. It may then be washed and brushed up with a soft nail-brush and soap and water, dried and mounted on velvet; or it may be "bronzed" with blacklead, or lacquered, if it is desired to preserve the beautiful surface it presents when first detached from the mould. The work or mould, if soiled with blacklead, may be cleaned with a soft tooth-brush moistened with benzine. It may be necessary after this to brush up with soap and water, using a fresh, clean brush.
When it is desired to produce a facsimile of the article to be copied, a trifling
modification must be made in the manipulation. This consists essentially in preparing, first, a wax mould or cast from the original, from which mould the copper electrotype is produced. To this end, take a strip of paper long enough to make four or five turns round the sides of the object to be copied. This must be bound round the edge so as to extend up above the face of the work to a height of nearly half an inch, and tied tightly round the sides. The whole should now be laid on a flat table, face upwards. Sufficient good beeswax to cover the face of the work to a depth of about jj, in. is now melted in a perfectly clean pipkin or ladle. The surface of the work and the inside of the paper binder are now heavily breathed upon, so as to prevent the wax adhering, when the melted wax is immediately poured in to a depth, as we have said, of about •% in. The mould should now be allowed to stand for an hour or two to set and harden thoroughly. The paper binder is then removed, the wax mould pulled off, three or four turns of No. 20 wire bound round the edge, and the surface and edge of the mould carefully blackleaded with a very soft camel-hair brush. It will not be advisable to wet the blacklead ; but, using fine powder, breathing on the mould will suffice to render the surface sufficiently adhesive to take a good polish. The blackleaded mould is now to be treated precisely as recommended for the reversed facsimile. In the accompanying diagram are shown sectionally the proper position and connections of dry cell, wire to anode, depositing dish, mould, and wire from mould to negative pole of cell. work was found to have been not even discolored—in fact it was apparently entirely unharmed. A facing of pressed brick is being substituted for most of the terra-cotta, but some of the latter will still be used on the lower stories. All of the floors must also be replaced.
The total damage to this structure was estimated at between 35 and 40 per cent of its entire cost. The photographs show it immediately after the fire (side view), and after the facing was removed and the brick work begun (front view).
A Unique Telegraph Office
ONE RESULT of the recent great fire in Baltimore was toburn all of the telegraph offices in the busiest part of the city. It was supposed that all of the wires extending to this section were also disconnected by the fire effects; but on the day after the conflagration, an electrician, making tests, found one wire which connected with New York City. A set of instruments was immediatelv secured. The wire ex
A Unioie Telegraph Station.
The first established in the "fire zone" at Baltta ore after the recent conflagration.
tended along the trunk of a fallen telegraph pole, and messages were sent from this novel telegraph station to the metropolis. This was the first office opened in the business district after the disaster. The accompanying photograph shows an operator sending a message.
Monster Circular Derrick.
is known as a circular derrick, and is operated entirely by electric power. It has actually raised a weight of over 150 tons, swinging it around a circle 147 feet in diameter. Loads weighing seventy tons have been lifted and swung in a circle of 207 feet. The derrick will lift the heaviest cannon to a height of 100 feet above the surface of the water, and yet its machinery is so simple that but two men are required to operate it.
This derrick is composed of a steel tower or framework carried on pile foundations. This tower, which is circular, is fitted with a track for the rollers that carry the movable or revolving portion of the derrick. The revolving portion consists of a heavily framed structure, circular in general form, and carry
Lifting Machine In Operation.
which engage with a circular rack fixed to the stationary tower or framework. Each of these pinions is driven by a General Electric motor, capable of developing 20 horse-power. The racking movement of the jib is effected by means of wire ropes leading over sheaves at the top of the jib, and wound on large drums, which are located in the revolving structure of the derrick. The inner and lower end of the jib has a pin connection to the revolving structure, so that, by winding up to the drum, the outer end is raised and is brought in toward the center, while unwinding the drum lowers the outer end and moves it out from the center. The hoisting blocks are carried, as before mentioned, from the outer end of the jib; and the leads from these blocks run clown the jib to drums, which, like the others, are operated by electric motors.
Dangers of Imperfect Insulation
THE USE of electrical apparatus is so prevalent that, as is well known, a large number of fires originate from the electric current. Investigations made by insurance men prove that much of the so-called insulation intended to protect inflammable material from the action of the electric current is so poor that it affords little or no protection, while some of the currents are of such voltage that ordinary insulation is no safeguard whatever. The accompanying photographs give an idea of the destruction caused by inadequate electrical work. The first photograph shows a number of fuse cut-outs which were placed on a 500-volt circuit. These were constructed with a porcelain base, but the insulation was not sufficient to prevent the current from communicating with wiring and woodwork about the cut-outs, with the result that a fire ensued which caused a loss of $25,000. While investigating the cause of the fire, the ex