give you the length for the bottom. Now take the circumference of the trap to get the size. Half this will be the width for you to cut the lead, which must be cut truly, and with planed edges. Next, just where the lid is to fit D, take the mallet and hollow your lead a little, not to thin the lead, but just to fit the bottom of the block, then offer it on the block and end up the inlet end; take the ring and fix it on this part of the block. Next bend up the part from D to A, and with the other ring fix it there, then with your tools (a bossing-stick will do) work the lead to the shape of the block, taking care to drive the molecules of the lead in the direction you require them to flow, and be sure that the lead is of uniform thickness; in like manner do the throat or top part. Care must be used to hollow and fit the lead to as nearly as possible the proper shape, by first turning it back, and with the bossing-stick well drive up the throat part, C in plan (Fig. 68). This will thicken the lead; after which place it upon the block and bend over the back to the out-go, and with the rings fix it there, then work it to fit the block.

I have before said this should be in two halves; this will give you a line to trim your lead to, should you require it trimmed off for soldering.

The next thing to do is to solder it up, which may be done with the copper-bit, wipe it, or burn it. The last-named is much the best.

S-Traps made in Three Pieces. This is a very old method of making -traps: the bottom QDF is cast, the dip M L soldered or burnt on, as also the out-go A Q J. A

FIG. 72.

M

Α

N

drawing of a trap weighing over cwt., lately
taken out of an old house in Knightsbridge,
illustrating this method, is shown in Fig. 72.
S-Trap with Lugs for Fixing above Floors
(Fig. 73).

Fig. 73 is a diagram of an or half trap for fixing above floors, suitable for short

or low balloon basins.

K

FIG. 76.

N

dip N, with rounded bottom and top; an air-
chamber B, which prevents waving out (the
great fault in the C-trap).

The Eclipse is cast in one piece of lead. Fig. This trap may be made with cleansing cap and screw, and can be wiped down to the soil-76 is the elevation of it, showing that the whole is rounded, which, in the estimation of many sanitary engineers, is a great advantage.

pipe at A, or on a straight outgo. This style of trap has been made in earthenware, but the difficulty has been to make the connection with the lead and outgo sound. This difficulty has been overcome by making the trap of lead instead of earthenware.

The Semi-Trap (Fig. 74). This is another trap for fixing above the floor line, and excellently well it answers its purpose.

V-Traps (Fig. 77).

This excellent trap is, in principle, part and part -siphon. Z is the cheek; T the throat; J the top, which also goes down to form the throat, and up, then over to the top to V; the top or inlet-pipe is soldered on last.

I shall now show the best method of making it, so that it shall be what is generally known as self-cleansing; at the same time I shall keep within the bounds of that principle, which, I suppose, is universally known to be the beauty of the O-trap-viz., the clearing the soil from the inlet to the body of the trap, and its retaining the water-seal or lock; especially against the waving out caused by strong currents

of air blowing down air-pipes or up soil-pipes.

Fig. 79 is an elevation of the O-trap, having side or cheek; this latter being fixed here, is a cleansing cap and screw C soldered into the

FIG. 79

The method of cutting out this cheek Z is as follows:-First strike the circle A, W, C, Fig. 78, draw the right line E K, cutting the top of the circle; next draw the line E, square to the top line, and cutting the circle at B; then measure off the outgo R, with the distance from E, to the extreme periphery of the circle at C; now, with a straight-edge, draw the outgo line R, to cut the edge of the circle, as at C, then draw WD square to the top and the slanted line Y D, taking care to go low enough at the throat more for sink work than for closets-in fact, the in order to have a good dip. Prepare this cheek proper place for this cap and screw for closetand solder on the band, as at KGA E, Fig. 77, work is at I. In order to get at it, I have made then the top, and dip in another piece, after-traps with the dip to screw in and out, but which, solder on the inlet-pipe L M. Of course the throat part and up TWZ to R is soldered from the inside, and the part RE after. Messrs. Beard, Dent, and Hellyer make a cast trap somewhat similar to this last described.

for sink-work it is best at the side or under the bottom, as at D, Fig. 80. This allows you to take such things as tooth-brushes, &c., out of the dip, which cannot pass into the body of the trap.

Fifthly Keep the dip-pipe close up to the presses flatly, so to speak, on the surface of the heel of the trap, as shown at N, Fig. 83.

The Action of the -Trap.

Junior plumbers will do well to notice the details of the action of the C-trap.

On lifting the handle W, Fig. 83, it brings up the lever H, with it the tumbler pin G, and the crank which works an axle having the loose

trap; thus, the so-called C-trap ceases to be a trap, and becomes only a snare.

This, I venture to suggest, is a sufficient reason for all sanitary engineers to condemn the -trap, and, until they can find something to supersede it, use the , which I must repeat and have already proved publicly, is the best trap yet invented.

(To be continued.)

THE WATCH AND HOW TO
REPAIR IT.

By SECONDS' PRACTICAL WATCHMAKER.
(Continued from page 564, Vol. XXXIII.)
Geneve Barrel-Ratchet Cover Screws
Overturn.

WA

make a

screws.

how seldom do we see the screws of ordinary "bell-metal" polisher about a quarter of an
watches clean and blue; but on the contrary, inch broad, charged with red stuff mixed with
their screw-drivers' damages, having slipped oil, pressed against the screw with the man-
from the notch and so spoiled it, that difficulty dril kept in motion until a smooth surface is
is experienced in screwing them firmly; there- produced. Then prepare a small piece of deal
fore, the following remarks, I hope, may enable wood with smooth surface, charge it with ordi-
any class of workman to repair damaged nary redstuff and oil, which should be used as
"screw heads ": polish them and blue them, so an ordinary polisher, after which the "notch"
as to be suitable for superior, as well as ordinary must be cleaned out again with the knife-
work.
shaped peg and redstuff; next it requires to be
carefully cleaned with soft bread, after which
the refuse polishing-stuff must be cleansed by
benzoline or spirits-of-wine. At this stage of
the process the dampness from the spirit should
be wiped off, and left a short time to thoroughly
dry. Then have a scrupulously clean brush, by
which the screw should be brushed, making use
of it in the direction of the "noteh."

In dealing with the subject, we will suppose that a new screw has to be applied, say a "potence-screw," which may serve any purpose of the series. The screw selected and fitted, the attention of workmen is directed to the points following. The soft screw has to be hardened and tempered; a good way of so doing will be to place it upon a piece of charcoal or pumicestone, and if convenient, it would be better to place it in a small hollow, for reasons that, when ATCH-jobbers are not surprised to find the gas-jet from a "blow-pipe" is directed to one or more of the Screws "overturn it, it may be protected from falling; and again, which should secure the barrel-ratchet cover, being in such hollow, it becomes "red-hot " and that portion of the hole which should hold more quickly than it otherwise would. Before the "tapped" portion of the screw, with no the screw is placed upon charcoal, a small piece thread in it, and too large to enable anyone to of ordinary soap should be put upon the "tap" make the hole suitable for a larger "tap." The of it, the object of which being, by the applisecurity of the ratchet-cover requires little com- eation of such, after having been hardened, it ment, because, by its soundness of securing the will be white instead of black, which enables ratchet, the firmness and upright of the barrel is workmen to observe the colour produced while maintained. When one or more of such screws it is being tempered. Many people "harden" "overturn," and the should-be "tapped" hole screws by making them "red-hot" by means destroyed, the best method to adopt is as follows. of a "blow-pipe," and "quenching" them in Having selected the quantity of screws required cold water; such is not a good way, because the with suitably sized " taps"-supposing that steel is thereby very brittle, while for such such are at hand without the trouble of making small things as "watch-screws" their toughness them-fit them into a hole of a "screw-plate,' is endangered. The best way I have practised so as to be enabled to have a size by which to is to quench them in oil; by the cold-water "tap," so that a new tapped-hole can method there is a saving of time for those be made by it which will suit the screws who require rapid production, because, from selected. Next make a "tap," which should be leaving the water, the screw may be tempered a trifle smaller at its point, with four sides to it. without any other preparation than merely which will serve to enlarge a hole that removing the water from it; whereas, when oil might be too small for the intended new is made use of, it has to be cleaned with "soft The screws, and the "tap" suitable bread," after which it must be placed in benzole to form the holes for them being prepared, or benzoline for three or four minutes. By the the old holes have next to be 66 'plugged.' process described the screw will be as hard as Such may be successfully accomplished thus. "flint," and must be reduced so as to be softer, Obtain some which is "bouchon" "stopping wire,' so rendered by placing it in a the hole of which should be such size that "blueing "-pan with end of the screw-tap the prepared tap" form a good thread upward, and then held over a gas-flame or in it for the intended screws, previously spirit-lamp" until the end assumes the colour to "plugging" the barrel-bar holes,-which blue-in which condition it is prepared for usually contain a small number of threads. The polishing. tapped holes to suit the screws being prepared, The colour produced upon the screw by the the next point should be to slightly taper" the act of hardening and tempering" has next to "bonchon-wire" with a very smooth file, it be removed, which is easily effected by means of Put the then can be fixed in a "pin-vice," and by the a "slip of oilstone" aid of a "screw-plate," a light thread can be screw in the " screw-tool" in such a manner formed upon it,-not a full deep one. The "tap' "that the edge of its "head" projects a trifle referred to should form a thread in the screw-above the part of the tool which secures it, clean hole of the bar, into which the "bouchon" out the notch with a thin good screw-head file. may be screwed; but, before the intended The edge of its head should next be polished by "plug" be finally fitted to such bar-hole, the the oilstone and oil, after which, the top-its length of it must be marked on by the edge of a head-proceeded with in a similar manner until very small and finely cut file, and placed in a the scratches are removed, which were the reThe "threads" of the screw next pin-filing" block, by the edge of sult of a file. groove of a a knife a slight ring can be formed corresponding claims attention, and should be cleaned, which to such as is general upon a "bouchon," which is effected as follows:-A piece of deal wood serves as a place to separate the required piece split half-way, and some oilstone dust and oil inwhen it has been tapped the proper length into troduced, place the screw-"tap" therein, put the the barrel bar-hole. When screwed in and wood into the bench-vice, closing it until it is broken off, the previously useless screw-hole will be firmly held, then, by means of good pointed filled up by a sound threaded tapped hole; but screwdriver placed in the screw-notch and in such a state it will not have reached its twisted forward and backward, will, in a tap " and the back finished condition, because a slight riveting of it minute or two, polish the " will be necessary; after which, the projecting of the screw-head quite bright; but it may happen portions of it will require removing by means of that the end of "tap may be unpolished. a small chamfering tool, such as an ordinary Polishing and burnishing it is the work of a "'hollow drill, which is used for the purpose couple of minutes. Put the screw into a tool of cutting the hollow for a new upper-pivot to termed a "lantern," revolve it against a cork When the "burrs," which the thread-or such-like fixed in the vice, polish with oil"cutting" operations produced, have been re- stone, brighten with a clean burnisher. moved, the screws may be finally completed, care The screw at this stage of polishing would be being taken to avoid forcing them into the holes, grey," and the next process will be to "gloss" using oil to the taps" for fear of loosening it, before doing which, the screw notch must the new plugs. All "tapped" holes should be seen to, that it is sufficiently deep, for should have the sharp edges removed by an ordinary it be very shallow, the power exerted by the triangularly shaped "chamfering" tool. screw-driver might slip out of it and spoil the appearance of its colour, which will spoil the final finish.

a verge.

66

To Polish and Blue Screws for Superior
Watches.

How seldom is seen in superiorily finished watches, after having been cleaned a few times, the screws of such without having been spoiled by persons who professed to clean and repair

them. Such persons, I believe, should be termed "Chalk-and-brush men," who do little else but brush out the dust and oil. Again,

66

"Arkansas." or

To gloss the screw-head," it must be seen to that, by "soft-bread" all previous dirt and grease are removed; an important point to secure as clean, is the screw-head "notch." When the screw has been replaced in the tool similarly as referred to, shape an ordinary "peg" in form resembling the cutting edge of a knife, with which clean out the "notch" with dry redstuff; then a

An important point must here be noticedviz., after the screw is ready for blueing, the sharp edges of the "notch" should have a burnisher passed from end to end of it, producing a slight bevel which somewhat prevents a burr from the blade of a screwdriver.

The burnisher next claims attention: it must be clean from a good board and flour of emery, and when the screw has been replaced in the screw-tool-having rubbed it upon clean leather, the gloss will appear by little rubbing and light pressure upon it. Having brushed it again, blueing is the completion of the process.

The screw-tap being placed in, say, a hole made in the bottom of an ordinary watchbarrel, which, when placed in a blueing-pan held over a gas or spirit-flame, any coloured hue may be produced: a violet is usually admired.

With a little care in proceeding, screws thus polished are the same colour all over, even the screw-notch.

Geneve Lever Occasionally Stop.

The instrument here referred to was useless

as a watch. To make use of a familiar phrase,
"It was always out of time," and had been
accustomed to such for years, and hence I am
induced to introduce the defect for it had but
When it was in general
pocket use" it
would mislead; but when placed in a stand
upon a dressing-table or such position with the
"bottom" of the case partially open, it would
serve its purpose well.

one.

After several weeks being in custody of a watchmaker, it was dis covered that the "spur" of the fly-spring of the case was, by the closing of the case bottom, pressed against the outer end of the escapewheel cock; the end of it was shortened, by which the watch was afterwards useful. The fly-spring spur, when pressed against the cock referred to, caused the escape pinion arber to be bound.

English Lever Stop through Cock-Screw. Very often watch-jobbers fail to be suffici ently patient when completing their work; instances so often occur to prove such. A lever watch of good quality was complained of as "often stopping." When the testing of it was introduced, the balance had no end-shake, yet it had been a useful watch until its last cleaning. To ascertain the cause why the balance-staff was bound, by the act of unscrewing the cock, it was observed that, as the screw was being "unturned" the cock had a peculiar undu lating motion, but its screw did not leave its place as it should; the cock had to be lifted from its position, and upon looking further, it was found that the screw passage-hole was too small, and that such hole had a good tapped hole in which the screw (when screwed down) was secured in it, and that, when it was removed from the cock, it overturned in the plate-hole. The defect was here, for, instead of a screw binding the cock to the plate, it was tight in the passage-hole and loose in the plate, by which the cock was loose, and its gravity caused it to rest on the balance-staff upper-pivot, thereby at times the "staff" had no end-shake. Another properly-fitting screw remedied the defect. (To be continued).

THE PARIS ELECTRICAL
EXHIBITION.—V.

OR projecting, aided by a reflector, is, uf light to a great distance, the course, the only available source of light; but for lighting up a small space, the very power

R

50mm. diameter. The current was always ob-
tained from Bunser elements, varying in number
from 6 to 35.

tion. In the present series of articles, I purpose to give an account of the theories and experiments of Sir D. Brewster, respecting this subject. They are recorded in his book on "Philosophical Instruments," to which I must refer the reader for full details; but as the book is out of print, and somewhat difficult to meet with, I trust the following summary may not be out of place in these columns.

of the electric are constitutes a great defect. The eye is dazzled, and it is impossible to work by this too-powerful light. Many attempts have been made to tone down the light, fur- With regard to arrangement of the experinished by regulators and candles. The simplest ments, which will be readily understood from way is to inclose it in a ground-glass globe; the apparatus described, it may merely be menmuch light is lost, but the result is much less tioned that the two Nicols, one of which was fatiguing to the eye. Room No. 15 of the behind the heliostat, the other before the therExhibition is very pleasantly lit up by Jaspar's mopile, were inclined with their principal system, in which the regulator is hidden in an sections not, as in optical experiments, about Brewster conducted his inquiry, with the opaque cylinder open at top. The light is 90°, but about 45° to each other, because thus view of finding what kinds of glass were most reflected on to a large white screen, suspended the working of a deflection is at its greatest suitable for the formation of object-glasses for from the ceiling, and is diffused into the room. (in optical experiments this angle is not taken, refracting telescopes; and although he did not I notice also the lampe-soleil, by Messrs. because the eye is less sensitive for large differ- succeed in meeting with a combination which Clerc and Bureau, which lights the picture-ences of moderate intensity, than for small was perfectly achromatic, yet he has shown in gallery just as sunlight would. It may be differences in the neighbourhood of nil inten- what way the greatest amount of correction briefly described as an electro-calcium light; sity). In the experiments the position of rest may be obtained. He made experiments with that is to say, the electric arc is inclosed in a of the galvanometer needle was determined be- prisms of a great variety of substances, and sort of calcareous crucible, which being raised fore the "diamagneticum" was brought between during the course of these investigations, many to incandescence, adds to the light and gives it the poles of the electro-magnet; then the mag- important facts connected with the dispersion a rich mellow tone, which is much appreciated netising circuit was closed, and the current sent of light were ascertained. There is probably by the public. There is no machinery in this in positive and in negative directions, once no other writer who has done so much for this lamp. The two carbons fall by their weight, as when the thermopile circuit was open, then special branch of optical science; and, so far as fast as they are used up, through the holes in the when it was closed. If the magnetising I am aware, there is no published account of a calcareous block. current had no effect on the galvanometer, systematic course of experiments in this direcand the needle with opened thermo-circuit re- tion, other than that contained in the book mained at zero, and with closed circuit at the above alluded to. The columns of the ENGLISH division corresponding to the heat-action, whether MECHANIC seemed peculiarly suited for the disthe magnetising circuit was closed or not, the cussion of the present subject; for it numbers diamagneticum was brought between the poles. among the readers and correspondents of its The position of the rest of the needle with open pages, men of the highest eminence in practical thermo-circuit was ascertained, then the thermo- optics. If my humble effort to bring the circuit closed in positive sense, and the deflection admirable work accomplished by Brewster into read, then the magnetising circuit was closed in more prominent notice shall succeed in directthe positive sense, and the deflection read; then ing attention to this subject, and thus elicit the magnetising circuit opened and a fresh read-other facts connected therewith, the object of ing taken. Then the magnetising circuit was these articles will be accomplished. closed in the opposite direction and the deflection noted; then again opened and the deflection produced by the thermo-current observed; lastly, the zero-position of the galvanometer needle was noted. When this series of observations was concluded, the thermo-circuit was closed in the negative sense, and the same series carried out. From the sum of the differences between the deflection when only the thermo-circuit was closed, and when this and the magnetising circuit were closed, both when the magnetic circuit was closed in positive and in negative sense, the electro-magnetic rotation of the plane of polarisation was deduced.

The incandescent lamps are also much liked on account of their soft light. Edison's lamp consists of a thread of carbon about 12cm. long and 1mm. section, inclosed in a small glass globe exhausted of air. The two ends of the carbon thread are coppered and fixed to platinum wires which are fused in the glass, and by which the current passes into the lamp. The thread is made of carbonised bamboo. In Swan's lamp it is of carbonised Bristol-board. The latter lamps light the Congress Hall, the small buffet, the British Post Office Exhibition, and the British Conmission. Those of the small buffet receive their current from Faure's accumulators. Maxim's lamp differs from the two others in that gasoline vapours have been introduced into the glass globe before exhausting it. The object of this is to renovate the carbon thread by a deposit of carbon on its thinnest parts. The incandescent lamps can give from a dull red to a brilliant white light (25 candles). C. Detaille.

These experiments were made with solid bodies, heavy and light flint glass, and plate glass,

In order to account for the unequal dispersion of the colours by different substances, Brewster formed the theory, that it was caused by the various refracting angles of the prisms which were used. But experiment soon convinced him, that this theory must be abandoned, and that the inequality arose from the particular action which each substance exerted on each of the several colours: yet it also became evident that a change in the angle of incidence or in the refracting angle of the prism, caused an alteration in the proportion of the various coloured spaces.

This was contrary to what had previously been considered correct-viz., that the dispersive power of a substance is constant for all values values

glass plates, viz:-sulphide of carbon, oil of tur-refracting angle of the prism into which it is
pentine, distilled water and alcohol. The results formed. But Brewster has proved beyond a
of the investigation are thus stated:-
doubt that this hypothesis is not supported by
1. In solid as in liquid diathermanous sub-facts; for he has shown that two unequal prisms
stances, there is an electro-magnetic rotation of
the plane of polarisation of radiant heat, and it
is always in the direction in which the current
flows through the spiral, or passes round the

the rotation is greater, the greater the index of
refraction of the substance.

ROTATION OF THE PLANE OF POLARISATION OF RADIANT HEAT. FTER Faraday discovered the rotation of magnetism, it was natural to make the same experiment with radiant heat. According to Naturforscher, Wartmann, who experimented with the heat-rays of a Locatelli lamp, inferred from his results a rotation of the plane of polarisation of heat; but several attempts of Parisian physicists, who repeated the experiment, were without success. Later De La Provostaye and Desains took up the question afresh, using magnetic core. sunlight instead of the light of a lamp, and 2. The amount of this rotation is, ceteris achromatic lime-spar prisms instead of mica-paribus, very different for different substances; columns in polarising apparatus. They also found an action of magnetism on the plane of polarisation, but the separate experiments showed no satisfactory agreement; besides, they were not quite free from objection, so that the question was still to be regarded as unsettled. Herr Leo Grunmach has lately made a new investigation of the subject, with the help of the more perfect instruments of the present, and he has succeeded "not only in proving beyond doubt the electromagnetic rotation of the plane of polarisation of radiant heat in several solid and liquid bodies, but also determined by quantitative measurements the dependence of the amount of this rotation on the nature of the substance, the intensity of the galvanic currents and magnetic forces acting on it, the length of the layer radiated through, &c."

In these experiments sunlight was exclusively used as the source of heat. It was reflected from an accurately adjusted heliostat and polarised by Nicol's prisms of uncommon size and rare purity, rendering measurements possible; (through ordinary Nicols only very small quantities of heat can pass). The heat-action was

3. With direct action of a galvanic current conducted round the diathermanous body, the amount of rotationis proportional to the intensity of the current.

4. In a diathermanous body placed between the poles of an electro-magnet, the amount of the rotation is proportional to the magnetic force working on it.

5. The amount of the rotation increases with the length of the layer radiated through, but the relation of the amount of rotation to the length cannot be numerically determined.

ON THE IRRATIONALITY OF THE
SPECTRUM IN ITS RELATION TO
THE ACHROMATISM OF OPTICAL
INSTRUMENTS.-I.

By "ORDERIC VITAL."
VERYONE who has seen the decomposition

of the same substance, may be placed so as to be practically achromatic, which could not occur unless the direction of the light and the angle of the prism, had some effect upon the dispersive power. This combination showed fringes of colour similar in character, but opposite in position, to those observed when prisms of different substances are made to achromatise. He calls this the tertiary spectrum, and proves that its occurrence is in exact agreement with theoretical deductions. With this brief introduction I must pass on to matters of detail; and first, it is necessary to explain what is generally meant by the terms

Refractive and Dispersive Power. When a ray of light falls on the surface of a transparent substance, the relation subsisting between the sines of the angles of incidence and refraction is expressed by the constant ratio μ. If and r represent these angles, then the deviation or change of direction which the ray undergoes is plainly (i − r) or

{Sin.-. Sin. )}.

measured by means of a sensitive thermopile, E of light by means of similar prisms of whose index is, is (-)). Thus the reactive

consisting of 25 pairs of bismuth and antimony different substances, must have noticed how
bars, and a Siemens mirror galvanometer. For
electrification and magnetisation of the bodies
through which the heat-rays passed, the author
used a spiral of insulated copper wire, 250mm.
long and 55mm. wide, and a very powerful
Joule horse-shoe electromagnet, with two
cubical armatures having axial perforations of

different are the spectra thus produced. Not
only does the whole extent of coloured space
vary in length, but also the space covered by
each particular colour, is in no two cases alike.
This unequal dispersion is termed irrationality,
and it has the effect of preventing two prisms
from forming a perfectly achromatic combina-

But if we take a very small value for the angle of incidence, these two angles may be considered as proportional to their sines; so that the deviation may be expressed by (urr) or r (-1). If the angle of refraction be constant, the deviation produced by any other substance index diminished by unity, forms a convenient measure of the refractive power; for it shows what alteration a substance causes in the direction of the original ray. In the optical formula for the foci of lenses, this quantity is an important factor; and in lenses of the same curvature, but of different media, the degree of convergence or divergence given to the rays