much beyond a perpendicular line drawn from the slit in the bench, so that when turned to one side or the other to change the position of the cord on the piece being turned, the arc which it describes in this movement should not be sufficiently prominent to cause the cord to wear by rubbing against the sharp corners on either side of the slit.

The Bow.

Advantageous use cannot be made of the pole, considered as the chief motor of the lathe, except when the dimensions of the workshop are large enough to allow its adoption without inconvenience. It is for this reason that many turners, and principally amateurs, replace the pole by the bow, arranged as shown in Fig. 38.

At the two ends of the bench, and near the middle of its width, two pillars are erected. These are of moderately hard wood, about 3in. square, and 3ft. to 4ft. high above the table, solidly fixed and joined by strong tenons, mortises, and pins. One of these pillars is partly shown, marked A in Fig. 38. Two brackets, E, placed near the top of these pillars, and joined in the same manner, support a bar, CC, of the same wood 2in. square. On this bar a shackle, D, made of metal or of sound wood, slides in a groove and receives the bow. This shackle is constructed in such a manner that the bow which passes through it crosses without hindrance under the projecting brackets, &c., any time it is wanted to move it towards one side or the other by sliding the shackle along the bar. If this shackle is made of metal, it is fixed to the bar, and also to the bow, by means of a flat-headed set-screw; if made of wood, each fixing is done by small wooden wedges.

The lathe bow is made in different ways, but we will be content to speak of those which experience has shown to be the best. Most frequently it is made of several steel blades made thin and spring tempered. These are placed lengthways, one over another, the shortest underneath, similar to the way in which carriage springs are made, the elasticity of which is well known. This form of bow is not made over 4ft. in length. Another is to make it of three or four blades of pine or of walnut placed flat ways, all of equal length, but each one diminishing to about one-fourth of its width and its thickness (see Fig. 39).

way

Again, it can be made of a single split piece of walnut or of ash, sound, and without cracks, diminishing all along, as in the preceding, about one-fourth of its width and of its thickness from the centre to the ends. The wooden bow, whether made in blades or of one piece, is ordinarily 6ft. long. The cause of this difference between the lengths of steel bows, and of wooden ones, is that the wood, naturally weaker and less elastic than the steel, should give, by greater substance and greater length, an equality of strength and of elasticity to those which are afforded by steel of reduced dimensions.

bench, and to fix in the top part of this into a solution of insoluble soap, such, for
pillar a strong foil blade, or a flat sword-blade, instance as ordinary Castile soap, having a
with its point hooked. This method has an quantity of alum incorporated therewith, and
advantage that the pillar may be taken away then drying the sheet by exposure to heat or
and replaced at will by fixing it under the otherwise, thereby forming a shell upon its outer
surfaces which will be substantially waterproof.
bearers by the means employed for fixing the The sheet is now treated in a bath composed of
poppets. There is another facility which is celluloid varnish, or other suitable compound,
obtaining a run of nearly 2ft., if care has which will impart an acid-proof coating to the
been taken to fix the blade, forming the sheet. It is evident that the coating of celluloid
spring, so that its point is higher than the varnish may be applied to only one side of the
place where the large part of the blade is sheet if so desired. After the coating last named
inserted in the pillar. But, as will be shortly has been suitably dried, it is evident that the
explained, all these methods are old, and sheet will be incased in a perfect waterproof and
are only mentioned here to make them acid-proof film, which, however, will be found
known to those who wish first to practise to have a comparatively rough or raw external
exclusively on the dead-centre lathe, and so surface, and as this would show in the finished
that they may be properly directed in any celluloid varnish on one side of the sheet a com
photograph, there is placed upon the coating of
purchases they may make. It is, moreover, paratively thick and smooth coating of barium
well to know them.
sulphate and gelatine, or a series of such coatings,
one superposed upon another, and of any suitable
The Footboard, or Treadle.
colour or colours; or this coating may be com.
The footboard or treadle, Fig. 40, has most posed of any other harmless material, such as
commonly the shape of an A, one leg of chalk, which will make a very smooth and
which is prolonged upwards a few inches, polished surface. The sheet is now passed
making it to the form of the Greek letter A, between polishing rollers, and is then ready to
and it is on this prolongation that the receive the sensitising solution or sensitive coat-
cord is wound. The construction of this foot-ing, which preferably consists of a collodion or
board is very simple, each one of the three gelatine emulsion of suitable nature, and this is
bars which compose it is joined by halving Three or more colours, either distinct or blended,
spread or coated evenly over the smooth surface.
or by tenons, mortises, and pins; care is
taken to round off the lower ends of the two may be brought out by coating the cards with
different coloured superposed coatings of aniline
longitudinal bars, so that these rest on the emulsions, one colour being applied after the first
floor of the workshop, and can move without has dried. Cards so treated present a very
tilting.
peculiar and pleasing appearance, as one colour
Some turners, instead of the A-shaped foot- melts away in the other. For landscape work,
board, or treadle, use a simple pine board, three or more colours may be employed, accord-
like Fig. 41, straight grained, about 5ft. ing to taste, or as the subject may require. After
long, 4in. wide, and nearly lin. thick. This drying, by heat or otherwise, the cardboard
board has a slot about in. wide at one sheet will be ready for the cutting or stamping
end for a distance of about 6in., to allow the machine, whereby it may be cut or stamped into
cord to pass, and for it to be wound around stamping' operation the cards may be provided
"cabinet, panel, &c., sizes," and during this
or unwound from either arm formed by the with the usual bevelled edges. Then, after
slot, lengthening it or shortening it as re-cutting up a large sheet into small cards, it will
quired. The other end of the board is cut be evident that the edges thereof will not be
off square and nailed to a wooden strip, about waterproof, and must be made so, unless the
1ft. long 2in. wide, and lin. thick, flat on waterproofing solution penetrated through the
the side on which the board rests, and thickness of the sheet.
rounded underneath. There are several
methods of making treadles, but this ex-
tremely simple work has no need of further
explanation; an inspection of the illustra-
tion will suffice to give a satisfactory idea.
This treadle being detached has the advantage THE general views given with thunder for
of being capable of leading the cord in all
the description of
positions, so as not to fret it against the sharp the first and largest tender which I have
edges of the bearers.
described. Fig. 107 shows the tender in outside
longitudinal elevation, and Fig. 108 in end
elevation, looking from the footplate.

MODEL LOCOMOTIVE-MAKING.

XXIV.

The second plate of illustrations which accompanies this, shows the following:Fig. 23, flat-top lathe bench; Fig. 24, flywheel; Fig. 25, wooden cross-piece to go between bearers; Fig. 26, left dead-centre poppet; Fig. 27, right dead-centre poppet; Fig. 28, wooden washer for poppets; Fig. 29, iron shoe to hold bar-rest; Fig. 30, wooden shoe to hold bar-rest; Fig. 31, side of deadcentre poppet fixed with wing nut; Fig. 32, end of same; Fig. 33, long iron coach-bolt passing through poppets vertically; Fig. 34, improved poppet by Valicourt; Fig. 35, movable cone point; Fig. 36, threaded barrel; Fig. 37, method of fixing overhead pole; Fig. 38, bow and frame; Fig. 39, bow made of three wooden laths; Fig. 40, foot-first time are as follows: Hand-pillar, K; steps, board or treadle; Fig. 41, simple foot-board, O; hook and draw-bars, P; and rail guards, Q L; flap cover-plate, M; tool-boxes, N; buffers, Fig. 42, turn bench for clockwork; Fig. 43, socket for T rest; Fig. 44, T rest; Fig. 45, socket with slotted base; Fig. 46, front of slider for slotted socket; Fig. 47, side of

In these views, AA is the outer framing, Article XX. p. 195; B B B are the axle boxes, forming the main longitudinals described in which, with their springs, wheels, &c., occupied Article XXI., p. 264; C is the tank and coal-bunker, illustrated in Article XXII.; D represents the various parts of the brake gear; E small buffers; F draw-link; G the hose-union; and H the cock and handle, described in Article XXIII.

Whatever material is used for making the bow, it is strung with a cord strong enough to make a spring equal to a pole. On this cord is a small boxwood pulley (not shown in the drawing), having a groove wide enough and deep enough to easily contain the cord. This pulley, bored through with a central round hole, is fitted by a small bolt with a riveted or screwed head to an iron spur, ending at its curved part by a rounded hook, supporting the cord which is attached to the foot board or treadle. The sides of the pulley are sufficiently near the KUHN'S inside curve of the spur to prevent the cord which bends the bow from getting between, but at the same time not so near as to impede the free rotation of the roller.

There is still another method of replacing the pole-less perfect than the bow, but which, nevertheless, has its usefulness. This is to erect a pillar on one end of the

same.

(To be continued.)

I need not make any allusion now to framing, tank, wheels, springs, and other parts already described in detail. But there are some appendages here shown for the first time, to which reference must be made.

Parts shown for the

In order to render the relations of the numerous parts more clear, I have roughly shaded the curved portions. Dimensions having been given previously, the shading will not be confusing.

The hand-pillar K on the right-hand side of the tender is like the similar pillar on the left hand side that acts as the brake pillar, and it i fastened to the side of the tender in a simila IMPROVED CARDS FOR way. Its use is to afford a grip to the han PHOTOGRAPHS.

SOME improvements in waterproof cards for

photographic purposes have been recently patented in this country by Mr. H. Kuhn, of Springfield, Missouri, U.S.A. The patentee takes a sheet of cardboard, preferably of such size as will make a considerable number of mounts, and renders it waterproof by dipping it

when climbing up the steps on to the tender. The steps L, two on each side, are cut fro bits of sheet-iron about in. thick, bent rour and riveted to the longitudinals A.

The flap cover plate M covers over the op space between the tender and engine, to preve the foot slipping between them. It is a strip thin sheet-iron, curved, and attached with th strap hinges to the foot-plate of the tender.

will then be stopped up with putty, and rubbe down with pumice-stone or emery cloth; then another coat of lead colour, to be followed by two coats of olive green, or red, or any colour that may be selected. Lastly, the panels will be lined out with suitable colours, and the whole covered with one, or more, coats of copal varnish. J. H.

By S. R. BOTTONE.

YOMPOUNDS containing gold readily

$19. COMP
part with that metal. A silver

print (previously washed in plenty of water to remove any free nitrate of silver), if immersed in a dilute solution of chloride of gold, gives up a portion of its silver to the chloride, and the gold takes its place in the form of a purplish-brown deposit. This mode of changing the colour of prints is known as "gold toning." A good gold-toning solution may be made up as folLows:-Chloride of gold, 1gr.; water (distilled), 10oz.; bicarbonate of soda, 3gr. The object of adding the bicarbonate of soda is to neutralise any free acid adhering to the gold chloride, this would tend to bleach the prints very much To use this solution, the prints, as they come out of the printing frame, should be washed in several changes of clean water, until the water shows no milkiness. The effect of this washing is to remove the excess of free silver nitrate from the surface of the paper; and this is essential: otherwise much gold would be wasted. The prints, having been well washed, should then be immersed in the gold-toning bath, one by one, and only a few at a time. They must be kept constantly moved about, and turned over in stand so far asunder as the centre of the forceps, or clips (§ 7); otherwise they will tone the solution, by means of a pair of whalebone rails, the guards are curved outside, as they unequally, and show patches of red and purple, The hook and draw-bar P are similar to the were in the locomotive guards, which they re-instead of becoming equally purplish all over. hook and draw-bar on the engine, but the length semble. of the bar is increased. Fig. 109 shows this in The strips and angles noted in Article XXII. the light tones become still lighter, while the The operator will note that in this toning bath detail, fitted to that portion of the framing are seen in Figs. 107-8 at RR and SS. shown in Fig. 85, p. 195. The hook and bar are The panels between R R and S S can be painted more heavily-printed ones, while losing also single forging. An indiarubber washer is differently to the strips and angles, and each

મૈં

those upon the engine shown in Vol. L. p. 236, Fig. 109.

All rights reserved.

somewhat in density, change their ruddy brown to a purplish brown, appoaching in the darker portions to a bluish-black inky tone. In order, therefore, to get a nice and evenly-balanced picture, in which the high lights are not washed out and the shades slaty, it will be well to overprint pretty deeply. Practice alone can teach the amateur how much to overprint; but, as a slight guide, he should watch the heaviest shadows, and when these show a tendency to metallic iridescence, or look as if they were "bronzed," the desired amount of over-printing is reached. Of course this rule is not applicable to all subjects, since there are pictures in which the gradation is very delicate, so that there is no pure white in the highest lights, and no pure blacks in the heaviest shadows; such pictures, of course, will not admit of "bronzing." The observant student will also notice that even if he remove away the gold solution adhering to the prints by washing in plenty of water, the toning" still continues some time after removal from the toning bath. This must be taken into consideration when deciding the time which the prints are to be left in the toning solution. When the prints have attained to nearly the desired colour, they must therefore be removed, again washed by passing into a dish of clean water, and finally fixed by immersing for five or six minutes in the fixing bath, made as described at § 12. Of course the same precautions with regard to keeping them moving by means of the whalebone forceps (which must not be the same ones which are used for the gold solution) must be observed, as when fixing untoned prints. When fixed, the prints must be washed in a running stream of water until all traces of hyposulphite are removed. This can be ascertained pretty accurately by licking the print, when the peculiar sweetish metallic taste of the double hyposulphite of silver and sodium will make itself distinctly perceptible if any appreciable quantity be left in the print. There are two chemical methods by which the presence of hyposulphite can be detected, and as it is of the highest importance, for the permanence of the prints, that every trace of hyposulphite should be removed, these methods will be

detailed.

$20. To detect the presence of hyposulphite, add a few drops of Condy's disinfectant fluid to a glass of clear water, just sufficient to give the water a pale rosy tint. (If Condy's fluid is not obtainable, a small crystal of permanganate of potash, which is the same thing in the solid form, can be used instead.) Place behind the glass a sheet of white paper, so that the rosy tint can be distinctly seen. Now allow a few drops of the water adhering to the washed prints to drop into the rosy solution, and note whether there is any change of colour. If the solution bleaches, or turns yellowish, there is still hyposulphite on the prints.

Another means of testing the presence of hyposulphite is to allow one drop of tincture of iodine to fall into a small wineglass full of water, so as to give it a pale sherry colour. If the drippings of prints containing hyposulphite be allowed to fall into this solution, the yellow colour will be discharged. In case, therefore, that either of the above tests shows the presence of hyposulphite, the washing must be continued, until at last no discoloration is produced.

§ 21. Prints thus toned, by means of gold, and carefully washed after toning, are fairly permanent-much more so than those which are "sulphur-toned," more especially if the paper on which the pictures have been printed contains no organic matter in the shape of size, gelatine, white of egg, &c.

FIG. 1.

SP, steam-pipe from the locomotive boiler; SV, stop-valve; S P, SP,, steam-pipes branching to each rotating steam-admission valve; C, cylinder; VG, VG,, valve gearing for working the steam. admission valve; VSI, VS2, valve spindles to which VG, VG, are keyed; VDS, VDS, (oscillating) valve-door spindles; EP, exhaust pipe; LA, lubricating apparatus; S, S, shaft to which piston, &c., are keyed; FW, flywheel, 4ft. diameter, specially fitted for taking the B.H.P. of the engine; BR, brake ropes; SB, SB,, Salter's (spring) balances.

$22. Many other metallic salts, besides the gold chloride, have the power of displacing the silver in a print, and substituting for it the metal originally contained in the salt. Many of these are of no practical use, either because the tone given by the substituting metal is not agreeable, or because the resulting tone is lacking in permanence. Among these may be classed mercury chloride and lead acetate, the former of which gives a rosy tint, the latter a slaty grey. There are, however, two salts which give excellent results. The first is chloroplatinite of potassium, which, if used in the following proportions, gives excellent results, the tone being of a delicate engraving black:

......

1 part 250 parts 1 part

Choroplatinite of potassim Water Nitric acid Before toning, the prints should be washed in plain water to get rid of the free nitrate, and, while wet, laid face downwards on a sheet of glass, over which a little of this toning solution has been spread. A glass-bottomed dish, roughly levelled, is admirably adapted for this purpose. A change of colour, or commencement of toning But since the whole of the silver in the print will take place almost instantaneously, and the is not substituted by gold (and apparently cannot print can be held in the hand and examined, or be entirely), it follows that gold-toned prints, if laid down, face upwards, on a sheet of glass, till exposed to an atmosphere containing sulphur in the toning is completed. This can be told by any form, such as that of rooms in which gas is all redness disappearing when the print is burned, or exhalations from sewers or other examined by transmitted light, and should not, decaying animal matter, especially if aided by in the case of the plain salted paper described at damp, will gradually fade. This is true of all § 8, take more than a minute or two. The prints in which silver enters as a component part. after-operations of fixing and washing are Hence a great deal of ingenuity has been precisely as described for gold-toned pictures, exercised in producing prints by means of metals with the exception that previous to placing in the other than silver, or by doing away with a fixing solution, the prints should be placed for a metallic basis altogether. Still there is a great minute in a bath containing a piece of common charm about a well printed and well toned silver washing soda, about as big as a hazel nut, in a print, and notwithstanding their tendency to pint of water. This is to remove any free nitric fade under certain given conditions of atmo-acid which would, as we have already seen (§ 17) sphere, silver printing will long remain a favourite, especially with amateurs, on account of its simplicity and certainty.

set up a decomposition in the fixing bath.
Prints thus toned appear to be even more
permanent than those subjected to the action of

chloride of gold. The above described process for platinum toning is due to Mr. Lyonel Clark, and may be found in extenso at p. 141 of "The Year Book of Photography for 1890."

BROWN'S PATENT ROTARY ENGINE.

VERY mechanic knows that if a thoroughly Food and lasting rotary steam engine could be devised, the well-known reciprocating machine would be speedily abandoned; but every mechanic also knows that there are great and almost insuperable difficulties to contend with before a long-lived (as steam-engines go rotary can be made. Amongst the many ingenious attempts that have been made, perhaps that which we illustrate herewith is about the best, and as it will at any rate interest our readers, the essence we give a description, with To those of of Prof. Jamieson's report. our readers who may not be conversant with the theory of the subject, it may be advisable to point out, as briefly as may be, that where it is desired to obtain rotary motion the object of an engineer would be to obtain a direct rotary movement in the prime motor; but hitherto that rotary movement has been produced by a reciprocating piston aided by a flywheel. A locomotive is required to run in one direction only at any given time; but to do that modern appliances, in the shape of pistons, have to move backwards and forwards in their cylinders, and their reciprocating motion is converted into rotary motion by the crank. How much simpler would it be if the wheels could be rotated by direct motion! That point has not escaped the attention of the electrical engineers, and in the fact that they can get direct rotary motion rests their chief claim to attention from locomotive mechanics. According to Prof. Jamieson, the chief points of novelty in connection with the rotary engine invented by Mr. A. F. G. Brown, of Swindridgemuir, Dalry, Ayrshire, are the cylinder, piston, and valves. The

A NEW PROCESS FOR RENOVATING OLD FILES, ENGRAVED STEEL PLATES, &c., BY ELECTRICITY.

HE above title will at once suggest to the lamps for old," and we must admit that at first sight the proposition to make new files out of old ones by electricity looks uncommonly like one of those outrageously ridiculous schemes with which our great-grandfathers were tempted in the old speculation days. Moreover, some of our readers will have heard of this new process before, and may possibly feel inclined to remark, "We know these files; they come from Sheffield." But they don't. Two years ago a paragraph went the round of the press concerning this very process, a patent having just been applied for. This paragraph in its peregrination got strangely jumbled. In one paper we remember reading that it was "a method of making files by electricity out of any old tools, introduced by an enterprising Yankee," and the "par." went on to recommend this hypothetical individual (for such he was) to take himself and his files back to Yankee-land, for the Britishers weren't as "durned" as all that. This paragraph was evidently not of the "inspired" order. The invention hailed from France, not America, and patent rights have been secured in all the more important countries by Mons. le Baron Augustin Personne.

But the fact that a baron is the patentee is no more likely to recommend the invention to the intelligent artisan than is its remarkable title. Perhaps the title and the name of the patentee might even be sufficient to "damn" it at once in the eyes of the man who jumps to conclusions. Hence, we had better at once state why we consider some description of it suitable to the pages of this journal.

There is in France a great society which exists for the express purpose of encouraging national industry; it is called La Société d'Encouragement pour l'Industrie Nationale. To this society any persons who are interested in industrial progress may be elected. The present year is the ninetieth of its existence, so that in point of age it is far ahead of our Society of Chemical Industry, and many other associations which are interested in promoting the progress of industry in this country.

The society was founded in 1801. It holds general meetings twice a month, and also special