no good if the insulation of line is faulty and the present aspect of telephony, and the
it makes "earth" anywhere except at the effect of the expiration of the controlling
ascertained. If the line is an overhead one, At the outset of telephony in this country
a break can generally be found by walking the two master patents, that of Bell for the
along the route of the wire; but if it is not receiver and Edison for the carbon trans-
visible, it must be tested for as just de- mitter, were acquired by the United Tele-
scribed.
phone Co. (now the National), who also
acquired all the more important subsequent
microphone patents, such as the Crossley,
Hunnings, &c. The patent they have used
is that of Mr. Francis Blake, and it is inter-
esting to note, as indicating the superiority
of the Blake as an all-round transmitter, that
the National Telephone Co., although the
owners of the other transmitter patents, have
never offered any other instrument than the
Blake to their subscribers.

wire perfectly insulated, which should now the line. This leaves both ends of the line only make earth at the "fault." We next proceed along the line wire to the most accessible place (preferably where we know there is a joint), and having arranged our detector and When testing for a "break" in an under- battery as in the previous case, we cut the ground wire where an earth return is used, line wire and touch the end of the wire the wire at one end of the line should be dis- from the detector, first on one side of the line connected, while the other is left connected and then on the other - the part which up to the instrument. One end of the line gives a deflection being the faulty wire. We thus makes "earth" while the other is in- then try at different places in the faulty sulated. We proceed to test from the end of part, cutting the wire at each place, till we the line that is put to earth. Taking the box containing the cells and detector, we proceed along the line to the first most accessible point, and dig up the wire. Having exposed the wire, we next get ready the battery and detector. First, one of the poles of the battery must be put to earth, which can be done by driving an iron rod into the moist ground, and connecting the wire from the battery to it. The other pole of the battery is then connected to one of the terminals of the detector, and to the other terminal is joined one end of a short length of wire. With a knife the covering of the wire to be tested is next removed, care being taken not to nick the wire or remove more of the insulation than is necessary to expose the copper, and the wire from the detector touched on the exposed place. If a movement of the needle of the detector is obtained the wire is intact between the place tested and the end of the line put to earth; but if no deflection is obtained, the wire is broken in this part. Care must be taken to see that the iron rod makes good connection with the earth. If the circuit is complete so far, we must proceed to the next convenient place and dig up the wire, having first seen, however, that the bared place in the wire is well insulated with first a layer or two of pure rubber, then a coat of rubber solution, and lastly well wound with prepared tape.

succeed in localising the fault. If a return wire is used it will be found somewhat difficult to detect the faulty wire at each place it is dug up; for this reason it is advisable At the next place we go through the same when laying the wires to tie a piece of tape test, and if the circuit is complete proceed to one wire at short intervals, thus allowing to the next, and so on until no deflection of it readily to be identified. With inside wires, the detector needle is obtained, when the of course, a different coloured wire is used break will be between this place and the one for the return; but this can rarely be done last tried, at which the detector showed a with underground ones. deflection. From this place we then work The Telephone Patents,-Before closing this backwards till the fault is found. It must series of articles on telephone fitting it VOL. LIII.-No. 1358.

The Bell patent expired on December 9th, 1890, and everyone is now free to use the Bell telephone-an instrument that can be used both as a transmitter or receiver. Few people were probably aware, until they came to try them, of the really excellent results capable of being obtained from Bell receivers, one of which is used as a transmitter. Practically speaking, by the expiration of the Bell patent, the telephone monopoly is broken down, since the majority of instruments are required for short private lines, and for short distances the results obtained by using two well-made, doublepole Bell receivers are but little inferior to those obtained from many microphone transmitters; while, moreover, from their simplicity they are in many instances to be and subsequent expense of maintenance. preferred, as being less likely to get out of order, besides being cheaper, both in first cost

The remaining patents, the principal one of which expires very shortly, relate solely to microphone transmitters, and below is given a list of these patents, and the dates on which they expire :

The Edison patent, by the expiration of which the battery transmitter will be thrown open to all, has been the subject of so much litigation, that it is, no doubt, familiar to nearly every body. It is on this patent that the United Telephone Co. took up their stand, and held so successfully, the sole right to use a battery transmitter in this country. The original specification contained some thirty claims; but by amendment and disclaiming, all these were renounced save the second, leaving the amended specification with but one claim, which is somewhat ambiguously worded, and runs as follows:"In an instrument for transmitting electrie impulses by sound, the combination with a diaphragm or tympan, of electric tension regulators, substantially as herein before described, for varying the resistance in a closed circuit substantially as set forth."

Numerous have been the attempts to design a battery transmitter that would elude this patent; but none were successful, owing to the difficulty experienced by the legal fraternity in defining a "diaphragm." Applied telephonically in reference to the Edison specification, it would appear to be anything capable of taking up the vibrations of the sound-waves, and, taken in this sense, it practically covers the whole field, whatever the shape or substance of the diaphragm. In the every-day sense of the word, neither Swinton's nor Silvanus Thompson's transmitter had a diaphragm, though both collapsed before the action of the United Telephone Co.

The Hunnings patent (the next in order

ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1858.

the Scientific Committee of the Royal Horticultural Society were awarded a Government grant through the Royal Society for the purpose of making an inquiry into the effect of urban Prof. F. W. Oliver fog upon cultivated plants. presented a preliminary report to the Scientific Committee on March 24, which deals almost entirely with the effects of fog on plants cultivated under glass. Information has been received from various parts, and apparently one point is settled-that country mists, as compared with urban fog, do little, if any, injury to plants under glass, even although it may be necessary to raise the temperature in the houses. The case is very different when urban fogs can reach the plants, and it was mainly the effect produced at Kew, Chiswick, and some large private gardens near London that suggested the desirability of making At Kew and at Chelsea the investigation. scrapings were taken from 20 square yards of the roofs of glass-houses which had been washed down well before the commencement of the spell of fog. In both cases the weight of deposit was about the same-31 grains per square yard, or six tons per square mile. An analysis of the deposit from Chelsea shows about 40 per cent. of mineral matter, 36 per cent. of carbon, and 15 the swell-case which is arranged to form the back | and that is effected by forming the flues of air- per cent. of hydrocarbons, which last item exfollowing The sulphuric acid was found to be nearly 5 per the swell-case in the portion of the top of the instrument. On the conveyors in the thickness of the material of the plains the oleaginous character of London fogs. front of the swell-case and facing the keyboard front of are placed the swell shutters h, which can be manner :-The lower part of the front of the cent., and the hydrochloric acid 1 per cent. operated in the usual manner by the knee of the swell-case h is made in three thicknesses, as From 2 to 3 per cent. of metallic iron in minute performer through the medium of a lever h, shown at o, o1, o' in Fig. 1 and 3, the inner thick- particles was also found a fact of some imlever h3, rod h, cranks hs, h, and rod h. The ness o1 having marked on it the lines of flues portance, for iron salts deposited on foliage are whole of the lower part of the case a is, nearly which take the direction that the ordinary metal known to be injurious. Prof. Oliver gives a For instance, up to the level of the keyboard, utilised for the air-conveying pipes would take; these are after-short account of what has been done, and of what bellows i, as shown clearly in Fig. 1, the feed wards cut out in any suitable manner, such as by it is intended to do, but many of the experiments being worked by two pedals, i, il, in the usual means of a fret-saw, as shown at p in Fig. 4, which and observations made are not yet ready for manner. An escapement valve (not shown) is represents an elevation of a portion of the thick-setting out in detailed form. The thickness o' is then glued between laboratory experiments have been made as to As to provided to relieve the bellows when fully inflated. ness. veneers of hard wood, and and sulphuric acid, in humid and dry atmospheres; Immediately over the bellows, at the back the two other thicknesses o and o2 of suitable the different effects produced by sulphurous portion of the instrument, is located the sound- material, such as board j, on which stands the third stop of pipes holes q are pierced where required at the ends of but the results are not yet available. j'inclosed in the swell h. The soundboard may the flues p within. These holes correspond with remedial measures, merely covering the houses be at any convenient level below the sound- holes r in the draw-slide m of the swell stop, with canvas mitigates the evil, as the fog is board e of the front pipes, so as to allow of em- and also with flues s in the soundboard j, which thereby to some extent filtered. Prof. Oliver ploying any required height of pipes j'. The is also made in three thicknesses with the flues hopes that some metropolitan grower will try the s', s, and s3 indicate the triple doors, and padded ventilators. A sugtwo stops of pipes d and e are worked with slidess in a similar manner to the lower part of the experiment of building a range with close glazing, k and in the ordinary manner; that is to say, front swell-case. be covered with a mantle of peroxide of hydrogen, horizontally, and immediately under the pipes, thicknesses of the soundboard j, the flues being gestion has been made to exclude fog from a the stop d being worked by the slide k and the formed in the thickness &, and connected to the house by fitting it with tricklers, so that it might stop e by the slide 1, and another slide, not shown, pipes j' by holes j*. It will be obvious that the flues p and s may permanganate of potash, or other absorbent, the two slides corresponding with the two portions-viz., bass and treble, into which the be cut to any curve, thereby offering less resist which could be collected in gutters, and pumped stop e is divided. But, according to the inven- ance to the wind than the ordinary jointed air-up again. There is an obvious objection to this tion, the swell pipes are worked by a slide m conveying pipes do, quicker action being given method that there would be much liability of placed vertically at the back of the divisions and a saving of space effected, the wood case of freezing, unless the temperature of the glass of short duration; but if they are persistent and over each pallet, and at a right angle to the the swell hitself serving the same purpose as a could be kept so high as to prevent that. Fogs, top of the soundboard j. All these slides draw balky part of the action of an ordinary organ. even when dense, appear to do little damage if with "hit and miss" holes in the usual manner, Also more room is left for the pipes to "speak' and are connected to the draw-rods n through ir, in proportion to the size of the organ. It accompanied by severe frost, the damage they the peculiarities of the atmosphere, and Prof. the medium of levers n', rods n', and bell-cranks will be understood that the improvements are in do to many plants is irretrievable. The character There being but one set of pallets, g, the part applicable to other pipe organs than chamber- of a fog will also depend to a certain extent on wind has to be "conveyed" to the swell-pipes, pipe organs.

circular tube runs forward, furnished with circular wick-holders. It is attached to the hinder end of the footplate with solder or with screws; there is no other attachment. The methylated spirit with which the lamp is fed may be poured into one of the wick openings, or an opening

CROSS SECTION
FIG 76

may be made specially in the top of the
rectangular reservoir, or at the hinder end.
Two splashers, K, are fitted over the driving-
wheels, and improve the appearance of the
They are held by two screws passing
engine.
into the foot-plate. They are castings, the
patterns being cut out in cardboard.

PLAN OF LAMP

FIC 77

It

A kind of bunker, L, is fitted at the rear.
is merely a bit of sheet tin, bent, and soldered to
the foot-plate.

A buffer-beam, M, is screwed to the front of
the engine. Into this, solid dummy castings, N,
O, are screwed at the hinder end of the engine.
to represent buffers, are screwed. Similar pieces,
These buffers, O, may be utilised for the purpose
of securing the spirit-lamp in position. Then
the bunker plate is made as a continuation of the
hinder end of rectangular reservoir for the spirit.
It is usual to cross-hatch the foot-plate proper
with the edge of a file, to represent a chequered
surface. This is seen at the rear of the engine,
and has a neat appearance (Fig. 75).

In the figures, P is the steam-tap, Q the water-
J. H.
tap, R the boiler-filler, S the steam-whistle,
referred to in the boiler article.

THERE

secured by wedges; but these are used exten-
be so held if desired. The objection is that glue,
sively in joinery, and the angles of sashes may
if exposed to damp, is not reliable; but close-
A mortise
fitting joints thus united almost exclude the
painted. White-lead, moreover, is often used
damp, especially if the work is subsequently
instead of glue for outdoor work.
intended for wedging is to be made as before,
and then is enlarged from outside by cutting a
wedge-shaped slice from each side, so that the
tenon no longer fills it up at this part. Two
wedges are then driven in on each side, or rather
all glued, they become firmly attached to and
each edge, of the tenon, and as they are first of

OTHER APPLIANCES. HERE are one or two items in respect to frame-making in general, as well as those for garden purposes, that it will be as well to revert to before carrying the subject in hand further. I have supposed that the angles of the sashes will be secured by pins. Now this appears form a part of the tenon, which becomes a doveto be a very simple matter, and yet it is possible tail, and cannot afterwards be withdrawn (Fig. 7). to do it wrongly; so much so, indeed, as to cause Now here again it is necessary to work rightly. the pins to keep the joints open instead of drawing The wedge must be exactly the same thickness them closely together. The proper way to do it as the tenon, with parallel sides, and it must be is to bore the hole straight through the part in cut as a long wedge, and only sloped on the side which the mortise is cut-i.e., through both bearing on the mortise, that which attaches to A short wedge is of little cheeks of such mortise-and then to put in the the tenon being left untouched, so that the wedge tenon, and with the same boring-bit just mark is, in fact, a right-angled triangle if viewed on the tenon for its own hole; then withdraw it, and either of its flat sides. instead of boring it precisely at that spot, make use in securing a mortise and tenon joint; but the hole just a trifle further from the end of such even without glue a long one takes a very firm tenon, nearer to its shoulder-see Fig. 6, where, grip of the work. however, the difference is exaggerated. When in this case the pin is driven through one cheek of the mortise, it must, in order to penetrate the tenon, draw itself in towards the shoulder, which will be able to do. Thus the mortise will be (being conical and rather smaller at the end) it itself drawn up quite snug and closely into contact with the shoulder of the tenon. No such drawing action will occur if the hole is bored It is not very often that outdoor jointing is through when the tenon is in its place.

A very general rule in framing is to make the tenons with a haunch or hanchion (Fig. 8). It is considered to prevent twisting, and to weaken the parts less. It is merely leaving the bottom measure is, as usual, taken on the line aa -i.e., as usual, and of the tenon of full width. In setting it out, the thickness, bb. It is then sawn the inside measure of the frame and the tenon is set out as usual with the square and striking knife, or a a-and the mortise gauge to mark its after the cheek pieces have been removed, the