The English Mechanic phosphorus to the ore while at a white heat it is not likely to supplant the simple carbon,

he could obtain perfect fusion and pour and the cost being altogether out of proportion mould the alloy into any desired shape. to the advantage gained. For electrical AND WORLD OF SCIENCE AND ART. For his special purpose Mr. Holland cast the purposes, however, the iridium is dephos

FRIDAY, AUGUST 8, 1884.

THE UTILISATION OF IRIDIUM.

ON THE PRODUCTION OF "TUNE
BANDS" FOR AUTOMATIC MUSICAL
INSTRUMENTS.-II.

runs at a rate of 3,500 revolutions per
minute. The iridium slips having been sur-
faced and drilled are removed from the
brass by the simple method of dissolving
the latter in acid, and the pieces are then
ready for use in the stylographic pens, after
they have been finally ground on copper
cylinders mounted on a mandrel run at a
rate of about 3,000 revolutions per minute.
Slitting or sawing the iridium is accom-
plished much in the same way, only in this
case the copper disc must be very thin, and
consequently it is of small diameter and well
supported by clamps on each side, while it
runs in a mixture of diamond dust and
cotton-seed oil, the latter being preferred
on account of its viscosity. Besides points
for pens the iridium alloy is used in making
draw-plates for the production of wires of
the precious metals. Wires of common
THE
HE instrument for dividing and mark-
metals are drawn through holes in a steel ing off the various notes and inter-
plate, but ruby plates are often employed vals of music on the paper bands consists
for drawing down gold, platinum, and of a base board a (as shown in the
silver into wires. The ruby is very hard, accompanying side view figure), 10in.
but not harder than the iridium alloy, which square. This has two longitudinal strips
has, moreover, the great advantage that it is of wood, b, at the margin in. deep;
not liable to splinter or chip by the rough the channel between these is exactly
handling or the heat engendered by the
drawing operation, which is about the best
example of intense friction. Iridium is also
used for the knife-edges of chemical
balances, and is steadily supplanting agate,
but in that case it is the mere edge, which
is firmly soldered to a brass piece attached to

By F. H. WENHAM.

phospho-iridium in sheets between slabs of phorised, by first heating it to a white in an iron, and breaking the sheets into irregular ordinary furnace, and then submitting it to pieces, soldered the latter to strips of brass, the electric arc in a lime crucible, which has and ground the iridium alloy to a flat the effect of removing the last traces of the surface by means of a copper lap charged phosphorus. Attempts have been made to ALTHOUGH some four years ago Mr. J. with diamond dust.. This copper lap is deposit iridium on base metals by the Holland, of Cincinnati, patented a about half an inch thick, and rotates at the galvano-plastic method, but not much method of working iridium, which we rate of from eight hundred to a thousand success has been attained, for, in the first described at the time, little seems to revolutions per minute. It is thoroughly place, it is difficult to procure sufficient have been done with Я metal which, annealed, and is therefore as soft as it can be quantities of the metal, and still more diffifrom its special characteristics, should made, so that when corundum or diamond cult to find a suitable solvent-or, in fact, be peculiarly valuable for certain pur- dust and oil is applied to its surface the any solvent at all-in the battery. Mr. poses. As most of our readers know, sharp and hard particles become imbedded in Dudley, of Cincinnati, however, believes gold pens of the best quality are tipped with the soft copper, and produce a lap which that he has found the best solution by placing iridium, as are some of the stylographic is capable of grinding iridium to a surface. an anode of the phospho-iridium alloy in pens, the extreme hardness and utter Drilling is accomplished in a somewhat contact with chlorine and common salt. indifference to acids of the iridium rendering similar manner, except that the hole is first Even then the anode does not dissolve fast it very useful for the purpose. Iridium is started with a diamond splint. As soon enough, and, though the experiments are generally found alloyed with either platinum as a little cavity is made, a drill fashioned kept very much as secrets, the best method or osmium, and the chief sources of the out of soft copper wire is brought into so far is believed to have been found in supply are the Ural mines in Russia and requisition, and the little cavity being fed treating the iridium or iridɔsmine to a precertain districts in California. It was first with diamond dust and oil, the hole is liminary process. It is mixed with common identified as an element by Smithson gradually worked through, though not very salt and raised to a red heat in a tube, Tennant in 1803, while investigating the speedily, in spite of the fact that the drill when chlorine is passed through the tube residue of the platinum ores dissolved in for several hours until a double salt of aqua-regia. It is white in colour, resembling chloride of iridium and sodium is obtained, steel, is about as hard as the ruby, and has which rapidly dissolves in water. From a specific gravity of 22:3 (that of gold that solution almost any desired salt of being about 19.5). When cold it is brittle, but iridium can be obtained, and in plating a at a white heat it is slightly malleable. It weak solution of sulphuric acid is found to is fusible only in the oxy-hydrogen blast or give the best practical results with the in the electric arc. Insoluble in all the double chloride of iridium and sodium, simple acids, it is slightly acted upon by though neutral and alkaline solutions also aqua-regia after the grains have been work very well. There is a promising field heated for some hours. Practically it for experiment in this direction, for a sucis not affected by anything but very cessful method of plating with iridium would special operations, and can be separated be very valuable. from gold by keeping the latter in a state of fusion and allowing the iridium to settle. Its peculiarities can be popularly explained by mentioning the fact that in Russia there is a law which makes it illegal to deal in or possesss iridium ore, and all that is extracted in working the platinum mines is handed over to the Goverment, and stored in the vaults of the Imperial Mint. The law was passed because, owing to the greater specific gravity of iridium, some smelters were in the habit of mixing it with gold in order to increase the weight, and, as it is difficult to detect it when mixed with gold dust, the Mint was not only defrauded, but put to considerable expense in repairing the machinery. In working the gold obtained from the mixed dust, the grains of iridium made indentations in the steel rollers, and marred and defaced the dies used for striking out the coins. Though the chief sources of iridium are the Ural Mountains and California, the metal is, in fact, widely distributed, but in the shape of platin-iridium occurs generally in the form of small cubes with rounded edges, and as osmiridium or iridosmine in flat irregular grains, or occasionally in hexagonal prisms. The goldpen makers examine these grains with a magnifying glass, and pick out those suitable for pointing their pens. These are soldered to the nibs and slit with a copper disc charged with diamond dust and cottonseed oil. Gold pens so finished are known the balance. The hypodermic needles of the difference in diameter would cause the paper as diamond-pointed, but, as a matter of fact, surgeon are also now made of gold tipped to deviate in a curved direction. They must it is a particle of iridosmine with which the with iridium, and in many cases where also be set exactly square, or at right angles nibs are tipped. The ore is first cleansed by extreme hardness is required with freedom to the line of the paper; if they are clearing it of particles of magnetic oxide by from corrosion the iridium alloy is coming means of a magnet, and it is then subjected into use. For the contact points of teleto the action of acids which dissolve out graphic and other electric apparatus iridium other impurities. After washing and drying is supplanting platinum, because it is found the dust is sifted, and the operator with his to last much longer and to be almost perglass and a needlepoint selects such grains fectly free from oxidation or sticking, while as are suitable for the penmaking industry. the points can be readily cleaned by rubbing A few years ago, however, Mr. Holland, with a piece of emery cloth. It will be in the being engaged in the manufacture of the recollection of our readers that iridium was Mackinnon stylographic pen, found it neces- tried by Edison for making incandescence sary to procure some larger pieces of iridium lamps, and it has also been tried with some than the dust yielded, and after many success as the negative of an arc-light; but experiments he discovered that by adding in both cases it may be safely assumed that VOL. XXXIX-NO. 1,011.

9in. wide, and serves as a guide for the paper bands required to be marked off. At the near end of the board two transverse steel rollers are set in bearings; these rollers are exactly 9in. long in the barrel part, and each in. in diameter. They must be accurately turned to fit a ring gauge, for any

a

d

oblique they will force the paper to advance sideways against one guide strip. These rollers are the same in size and mode of action as the feed rollers in the automatic instrument. The necks or bearings of the rollers are in. in diameter, and at the righthand side of the instrument are geared together by pinions, and revolve simultaneously. Woolen bearings or sockets are sufficient for the necks of the rollers to pasa through; but the top bearing or strip is prolonged to d, and secured downwards by a screw.

the wires indiarubber washers are placed so that the pressure between the rollers may be regulated, and they can separate so far as to allow for various thicknesses, or a joining or seam in the paper to pass through. The left-hand axis of the bottom roller extends out in. and has a flat filed on it. This is to receive the counting wheels. These are mere blank discs, about 2in. diameter, fitting tight on to the projecting axle of the roller, so as to turn with it. The discs are further secured by a milled-head screw, tapped in the end of the axle, which also attaches a wooden disc 24in. in diameter, with rounded edge convenient for twisting between the finger and thumb of the left hand. I do not require more than four removable discs, divided on the rims respectively as 7, 10, 15, and 20. The divisions are merely shallow V notches into which a spring strip drops, so that the click of the count can be both felt and heard by turning either way. The end of the roll of paper is first passed under a crossbar at the further end of the board which serves to keep it down between the guide strips, and is then entered between the rollers, and will, of course, be advanced in equal steps at each click heard or felt by turning the outer wooden head.

next.

Close to each bearing of the rollers is a to make the third or middle line stronger rudimentary treatises or catechisms of music. screwed wire, e, fixed in the lower bearing than the others. A light dotted line is it is only necessary to state that one division block, and passing loosely through the taken as a perpendicular from each of on each wheel represents the shortest note. holes in the top one. Under the nuts on the notes or holes in the scale to in-or a demisemiquaver and 32 divisions the dicate their position on the leger lines. longest, or a semibreve, of course having The notes in this are marked by con- regard to the value of dotted notes, rests, spicuous black dots, just as in music, but &c., by counting accordingly, leaving such dotted lines as represent the As an example of the mode of setting off intervening flats or sharps as blanks. The a piece, I take the first bar of a valse in end of each dotted line terminating above the opera "La Chatelaine." This begins in the scale and representing a natural, is the natural key, which has to be changed marked with its respective letter, and if the several times during the piece. Mark M.f. scale extends to several lines above or below in pencil for the expression of the bar. The the others, it is as well to put numbers to first note to be pricked off is A in the treble, these lines as conspicuously as possible, just a quaver; at the same time a crotchet in the above the pricking holes. Also in the bass, C, is marked through the paper. We middle of the scale the notes "borrowed" now count four as the value of A. Next, by the treble from the bass, or the reverse, G, a quaver in the treble, is marked off. We should be marked off above or below the count four more on that; this makes up the main lines extending to g in both cases. count of eight for the C in the bars. Next For the ready reading of 8va. in the treble, comes a quaver, F, in the treble. This is an a supplementary strip may be laid over the accidental sharp; therefore prick it off scale, so that without the necessity of through the hole on the right of the natural. pausing to reckon up the octave, the notes Simultaneously with this is a chord of may be pricked off from the lower supple- crotchets in the bass, E, C, and F, which mentary scale just as read in the music must be pricked off at the same time. Again, Having now described the only instrument count up four clicks; next, mark off Fa that is necessary for copying the music, I quaver in the treble. Count four, which will proceed to give particular directions again equalises the eight in the bass; then for doing this. mark off A in the treble, with a similar chord Having passed about two inches of the as before in the bass. Count four again, end of the paper band through the rollers and finally mark and count b in the treble, of the instrument, the proper division wheel and this finishes the bar, containing 24 has to be adapted suitable for the piece of counts; draw a pencil line across and two Over the paper, close to the rollers, is laid music to be copied. I can give no precise diverging lines, forming the acute angle rethe composing scale, this lies as a loose fit rule for this. Generally the counting presenting the "crescendo expression, between the guide strips, but is prevented wheels with the fewest divisions are not extending from this bar throughout the from touching the rollers by two side employed for the slowest music, composed pins within the strips; the scale can of long notes, which may be counted with To complete the illustration Iomit two bars, be slid back the other way and removed short divisions; the wheel must be and take the fourth onwards. This begins instantly. This scale consists of a plate used where the shortest notes, or demisemi- with a crotchet in both treble and bass, of brass, perforated near to its front quavers, frequently follow each other in the E and A. Count eight; next, prick off the edge with a straight row of holes, exactly piece. With any other wheel they would chord of crotchets in bass; this is equalised corresponding with the position of the cut too close or run into each other, so as to by the absence of a note in the treble, which keys of the instrument in which the cause a jumble. The wheels of 10 or 15 is filled with a crotchet rest. Next appears music band is to operate, and the scale divisions are the most generally suitable; a quaver rest in the treble, and beneath it a must correspond with the proper notes that with 20 may be taken for very slow chord of three crotchets. Count four as the therein. My instrument includes six octaves airs composed mainly of the longest notes. value of the rest; then are two following running through the chromatic scale, and, Having selected and screwed on the semi-quavers in the treble, C and G. Count consequently, has 71 keys spaced in. division wheel, the key in which the two on each of these, which again finishes apart. The holes in the composing scale piece is marked has to be set right on the bar of 24 count. Draw the cross line, need not exceed th of an inch in diameter; the composing scale. Supposing the key leaving marks in P for the expression at the below this and underneath the paper is a is in three sharps, viz., E, F and G. All the end of the bar. Throughout this piece the strip of brass, having a similar row of holes holes of the natural notes throughout the key has to be altered several times on the drilled through, so that when the composing composing scale, both in treble and bass composing scale; this must never be overscale is laid in place on the paper by being marked with these letters, are to be stopped looked. brought against the stop-pins the two sets off by turning the wire buttons over them, When an accidental appears as a natural of holes correspond exactly. About fin. and the sharps are to be pricked off to the note that is covered for the scale in which above all the holes belonging only to the right of each stopped note. If the key were the piece has been set, instead of turning natural notes in the scale a series of smaller in flats the marking would be taken to the back the wire button, it is better to push holes are drilled for containing-shaped left hand. away the scale (which is provided with two pieces of wire flattened on the tops. These The counting is reckoned entirely on the projecting milled studs for the purpose), are slightly flush riveted through the plate value of the individual notes, without re-and prick the hole under the edge just of the composing scale, so as to turn with a ference to the bars into which the music is below the natural note; the point of the wire slight degree of friction. These, when divided. These are merely for the purpose will find its way in place through the hole twisted partly round button-wise, cover the of abbreviating and facilitating the work of in the bottom strip under the paper. holes of the natural notes in accordance with counting notes of music when played by The examples that I have given demonthe key of the piece to be copied. This pre- performers directly on the instrument, as it strate the ordinary course of using the vents the possibility of pricking off a natural would be an exceedingly difficult matter for instrument; the principle of counting is just in place of a flat or sharp. The first, of course, a musician to reckon up the value in time that adopted by musical composers, for the being marked off at the left of the stopped of every individual note during performance. counts in the bar must correspond and be natural, and the sharps taken at the right In many pieces that I have set out on paper an equivalent in both treble and bass, the hand. The pricker is merely a piece of steel bands I have not taken any notice of the notes are sometimes curiously interwoven, wire hardened at the end, and whetted on bars, as they have nothing to do with the especially in duets, and blanks in treble are an oil-stone to a triangular point. This effect; but still it is desirable at the finish occupied by bass notes, and the reverse; but wire is set in a convenient thin handle with of each bar to draw a pencil along the top these places must always be attended to. a bulbous top. When the pricker is pushed roller, and make a crossline on the paper, as The learner, by a little consideration, will with a slight twist into a hole in the com- this enables a place therein, correspond-speedily understand and overcome all diffiposing scale, it easily perforates the paper ing with the music, to be more culties. Some passages may occur, at rare as the point passes freely into the corre- easily found, and is the means of at times, in which the counting is apparently sponding hole in the lower strip beneath the once detecting any error in the count, disturbed, and which cannot be met by paper. for, in the general run of music, the bars counting the clicks on the wheels. I have now to explain how the compos-make equal divisions, and if a bar just example, as in a piece containing triplets ing scale is to be figured, so that the place where three notes have to be counted as two. of a note can be seen at a glance without This may be done by an approximate sight any time to be lost in considering: First, division between the regular ones, or if the the five usual main lines are marked or operator wishes to be very particular, and a cut along the whole length of the scale, number of triplets appear throughout the sufficiently above the pricking holes to improvise 8 piece, he may suppleallow room for any bass or treble notes mentary division scale on a strip of that may be below the scale, I prefer card fixed inside one of the guides,

finished appears either wider or narrower
than the others, it should be counted over
again, and the error corrected, which would
perhaps otherwise have to be rectified by
cutting and rejoining the band.

It is unnecessary for me here to repeat
the symbols and duration of musical notes,
which can be best learnt from the common

For

reading off these irregular divisions by the quired; and so serious an outlay could only be on a water bath. When dry, carefully unfold passage of a pencil mark made on the paper contemplated by those who are large dealers the filter over a quarto sheet of stiff glazec when the count of the triplet begins. At in these substances, or who are desirous of paper: with a feather brush off every par first an "appoggiatura," or other expression, becoming and following the profession of "practicle of the precipitate adhering to the filter where the note has to be split up into several tical chemists." short ones, may appear as a puzzle in the counting; but these must not make any difference in the entire count or time, as in the first case the supplementary notes are taken as short counts in the time of the note that they precede, which, so to speak, is thrust back to make way for them, and is counted so much shorter accordingly, unless accompanied by a pause symbol, in which case the copyist may use his own discretion.

I. Paints.-White Lead (dry).
We take paints first for obvious reasons: (1)
the manipulation is comparatively simple; (2)
they are largely adulterated; and (3) they are in
general use.

White lead is now very seldom sold in the dry
state; but samples are occasionally met with.
Its covering power being superior to that of any
other known paint, it is very largely used; and
it is frequently adulterated with substances of
inferior quality. The most common adulterants
are sulphate of baryta and chalk.
1. QUALITATIVE ANALYSIS.

2. (Insoluble silicates.)-If no green colour appears the insoluble is a silicate. This may be proved by forming a bead with microcosmic salt on a loop at the end of the platinum wire, and taking some of the precipitate on this bead, fusing it again in the blowpipe flame. If small infusible particles whirl round within the bead while in the flame, the presence of silicates in the precipitate may be inferred.

From the above description, all this may appear very difficult and tedious in practice, baryta.)-Treat a small quantity with dilute (Sulphate of but it is really not so; it has all the charac-nitric acid, and heat on the sand bath. If any ter of a charming occupation. In a case in insoluble remains, it is either sulphate of baryta which I have given instructions, in only one or insoluble silicates. Filter; take a portion of lesson, to a lady in my household, the the insoluble on a piece of clean platinum wire learner has far surpassed the teacher moistened with hydrochloric acid, and test at the in rapidity of execution; the clicks blowpipe. If the flame be coloured green, the of the count wheel go on rapidly precipitate is sulphate of baryta. By moistening without intermission, and a mistake the wire in hydrochloric acid the green colour is seldom or never occurs; but the lady reproduced many times. in question has had the advantage of a musical education, and is, of course, familiar with musical notes, and, therefore, reads them with facility; but in this composition the recognition or reading notes by means of their letters soon ceases, and they are recognised at a glance by their position in or outside the lines. In my opinion, copying the notes by means of this instrument and the composing scale, can be done much more speedily than if the same notes or piece of music were to be copied by pen and ink. Whether the instrument in which these tune bands are to be used is capable of rendering all the expression contained in the piece, or not, it is just as well to note down all the words and symbols as they occur, even for the sake of reading up the holes in the paper for the purpose of discovering any note out of place, which may be soon acquired after their appearance has become familiar. These directions are somewhat brief because I have not dwelt upon the subject of musical notation, which is fully described in various rudimentary treatises. In my next I will describe the method of perforating or cutting out the paper for

the various notes.

SIMPLE EXERCISES IN TECHNICAL
ANALYSIS.

By AN ANALYTICAL CHEMIST.

3. Chalk. The presence of chalk can only be
ascertained after separating the lead. This is
best done by adding ammonia solution to the
of ammonia in excess, and boiling for five
nitric acid solution until alkaline, then sulphide
minutes. Filter off the black precipitate which
is formed, and to the filtrate, first tested with an
additional drop or two of sulphide of ammonia to
insure the removal of the whole of the lead, add
ammonic oxalate.
white precipitate
appear, it is calcic oxalate. Test a portion of
this precipitate at the blowpipe. A brick-red
colour imparted to the flame verifies the presence
of chalk.

If a

4. White Lead.-The presence of lead should be ascertained. This is indicated by the black precipitate given with sulphide of ammonia. It acid solution to expel the free nitric acid, adding may be best ascertained by boiling the nitric dilute sulphuric acid to the clear solution, dissolving the white precipitate of sulphate of lead thus formed in ammonic acetate, and adding potassic chromate to this solution. A heavy yellow precipitate (chromate of lead) forms when lead is present.

paper, collect the precipitate on the glazed paper, again using the feather, and cover over the precipitate with the funnel. Fold the filter paper till it assumes the appearance of a solid cylinder about one inch in length, wind it twice round with platinum wire, and ignite with the Bunsen burner over a weighed platinum or porcelain capsule. After a while the filter paper becomes a charred mass of smaller dimensions, and drops from the wire into the capsule. The wire is cleaned into the capsule, by means of the feather, of any adhering particles, the charred paper is crushed with a glass rod, and ignited over a Bunsen until the ash is no longer black. The precipit ste carefully transferred from the glazed capsule is then stood on a porcelain slab, and the paper into the capsule-the feather being employed to remove the last traces. The capsule is then ignited over an Argand burner until the weight is constant. The filter paper must always be ignited before the bulk of the precipitate is transferred to the capsule.

7. White Lead. The nitric acid solution obtained above is boiled nearly to dryness; and if a precipitate forms a little water is added, then dilute sulphuric acid in small quantity, and the boiling continued for some minutes to expel the last traces of nitric acid. An excess of sulphuric acid is then added, to precipitate the whole of the lead and lime as sulphates, which appear as a white, heavy powder. The beaker and its contents are then cooled by immersion in cold water; when cool double the bulk of alcohol is added, and the whole allowed to stand for some timeover night if possible. It is then filtered and washed with alcohol until the washings are no longer acid, dried, ignited in a porcelain capsule, From the weight obtained deduct 05 grain-the amount of ash and weighed as above. contained in an ordinary Swedish filter-paper, the remainder multiplied by 5 for the percentage of sulphate of lead, and (if no chalk is present), this again by 8525 for the percentage of white lead. If the sample contains chalk, the percentage of white lead must not be estimated until the percentage of chalk is determined (see below). The percentage of chalk is converted into its equivalent of sulphate of lime; this latter, deducted from the percentage of sulphates of lead and lime, and the remainder multiplied by 8525 for the percentage of white lead.

is to divide the nitric acid solution obtained above 8. Chalk.-The readiest way to estimate chalk into two equal parts; in one estimate the lead as above (multiplying the weight found by ten instead of five), and in the other estimate the chalk. The lead is removed with ammonic sulphide in the manner described above; to the clear filtrate ammonic oxalate is added; if chalk is 5. QUANTITATIVE ANALYSIS.-Insoluble sub-present a white precipitate of calcic oxalate is. stances. (Sulphate of baryta and silicates.)-produced. This precipitate is assisted in its Take 20 grains of the sample, treat with dilute separation by boiling, then collected on a filter, nitric acid as above. The quantity taken for ana- wushed with hot water, dried, and weighed. The

WE propose to give to our readers a few short lysis may be weighed in a watch glass or a small

papers on the methods ordinarily used for the detection of adulteration of the substances with which the English Mechanic is most familiar. This adulteration, being the work of experts, can rarely, if ever, be detected, and its extent estimated without the aid of chemical analysis. The writer of these articles was himself the victim of what he considers a serious fraud on the public generally. He sent to a local tradesman for some white lead of best quality. On its arrival its appearance aroused his suspicion, and on examination he found it to be a mixture of sulphate of baryta and chalk, but not a trace of white lead could he find. The tradesman assured him that he sold the paint as supplied, but bought his stock in such small quantities that he could not afford to pay 5s. for analysis. He was entirely at the mercy of an unscrupulous wholesale dealer, who made him (the local trader) the medium of dispensing his sophisticated rubbish. There is at the present time no articles more extensively adulterated as those sold by oil and colourmen.

basin; but should be transferred to a beaker, and
the glass or basin washed with distilled water,
before the acid is added. If this precaution be
not taken, and the acid added directly to the
watch glass or basin, to be washed into the
beaker afterwards, the violent effervescence which
takes place on the addition of the acid will
occasion considerable loss by spurting.
spurting.
If after heating with nitric acid an
insoluble remains, a few crystals of
chlorate of potash may be added to the
boiling liquid to insure the solution of all soluble
substances. The boiling is continued for a few
minutes; then cold water is added, and the whole
passed through a filter. The insoluble on the
filter is washed with hot water until the water
leaving the filter is no longer acid to litmus paper.
It is then dried on the water bath, ignited, and
weighed. Test at blowpipe as before. Sulphate
of baryta and silicates, if both present, are not
usually separated.

ignition is complete when the contents of the

capsule assume a tinge of grey colour. The weight obtained after deducting 05 grain for filter ash is multiplied by ten for the percentage of chalk.

In inexperienced hands it will be better to ignite strongly and weigh as lime, multiplying by 10 for percentage of lime, and by 1.7857 for percentage of chalk.

This chalk may be converted into sulphate of lime by multiplying by 1.36, and the product deducted from the percentages of lead and lime obtained above, prior to calculating the percentage of white lead.

The chalk precipitate should be tested at the blowpipe for its characteristic brick-red flame. 9. Some analysts treat the mixed precipitates of sulphates of lead and calcium with concentrated solution of ammonic acetate, and weighing the insoluble as chalk. This method is unreliable. White Lead (mixed).

6. Weighing Precipitates. This general 10. The oil must first be burned off, and To follow these exercises it will be necessary direction applies to almost all precipitates. If the ignition continued until no black carto possess some slight knowledge of chemistry strong acids, or acid and chlorate of potash are bonaceous matter remains. It must be ignited and of some of the materials used by chemists; used, the liquid should invariably be diluted before in a porcelain basin over an Argand, turned but any intelligent person can, by careful reading filtering. In washing allow the whole of the low at first and gradually raised. The of these descriptions, test substances qualitatively wash water to drop from the filter before adding ignition must be completed over a Bunsen. (which will be sufficient for most persons), without more water. When thoroughly washed, fold Much time is saved, and the analysis rendered the aid of expensive apparatus or external assist the filter paper flat in the funnel, or, better, more accurate by spreading the mixed paint in a ance of any kind. For quantitative analysis a transfer the filter paper and its contents to a thin layer over the bottom of the basin; and delicate chemical balance will of course be re-large watch glass or flat basin, and dry when the ignition is nearly complete by crush

ing the scaly crust with a glass rod, carefully removing the adhering pieces on the glass rod by means of a feather. The difference in weight, before and after ignition, represents the oil, plus loss by reduction of white lead to metallic lead. The residue is washed into a beaker with water as before, and afterwards with nitric acid. The metallic lead which adheres strongly to the bottom of the basin must be rubbed vigorously with the end of a glass rod until entirely removed. This requires a little patience, but it yields to persistent rubbing. The remainder of the process is the same as in the case of dry white lead.

THE DISTRIBUTION OF HYDRAULIC
POWER.

HE short note on p. 499, in which it is stated
contemplate the extension of their system of
mains from the City to Westminster, may pos-
sibly be the first intimation to many of our
readers that there is in the City of London a
system of hydraulic distribution of power which
has been extensively patronised by the principal
merchants having warehouses within the area
covered by the Company. Hydraulic power has
long been used at the docks and at the railway
yards in. London, but it is only within a
very recent period that power of the kind
has been distributed to private users-has been
laid on, as it were, just in the same manner as
gas is supplied. Probably the best installation
of hydraulic appliances in London is to be seen
at Broad-street Station, where, as a rule, four
out of a plant of six steam-engines and pumps
are almost constantly running to supply the ac-
cumulator which, in its turn, furnishes power to
the capstans, cranes, lifts, and other hydraulic
appliances with which the goods station is fitted.
The pressure employed is, as a rule, 7001b. to the
square inch, and the visitor to the engine-room,
if he happens to be unacquainted with hydraulic
machinery, is surprised at first with the ap-
parently eccentric behaviour of the steam-
engines for at one moment he may see
them running along at a
rapid rate,

and

when it is stored in the working tanks. The
pumps deliver into two accumulators 20in. in
diameter and 23ft. lift, loaded to give a pressure
of 700lb. to the square inch in the mains. There
are two sets of pumping engines, each capable of
indicating about 160 horse-power, already in
position, and another set is in course of construc.
tion. The engine-house is designed to accom-
modate six such sets when the system is fully
developed.

on the nose, or the apparatus may be attached to a cap or other head piece. The lighting apparatus is mounted on plate a by a ball-an 1-socket joint c, the balle being attached to a plate d, which may or may not be furnished with a reflector, and which forms the end of a cylindrical casing, upon which fits a tubular socket f, carrying the source of light, preferably consisting of an incandescent lamp. to whose terminals g are attached the wires from a battery or other generator. The From the pumping-station a network of mains socket f carrying the lamp is fitted upon the extends eastwards, embracing the numerous cylindrical part e, and a tube h carrying a lens blocks of warehouses situated in this district. is fixed in the end of tube e, the rays being The north side of the river is supplied by two directed either in parallel.converging, or diverging arterial mains which run along southwark- lines, by suitably adjusting the tube h in part. street and across Southwark-bridge, one being The conducting wires may either be inserted in and the other with Cannon-street. From these of an incandescent lamp any other kind of lamp connected with Upper and Lower Thames-street. the band b or be otherwised arranged. and instead the principal streets of the City are served, the may be employed, the parts being modified to connections being so arranged that in the suit. The apparatus, besides being employed for majority of cases each fed from either end. Thus, if a leak occur at some part of in mining, travelling, and for other purposes, as it, the faulty portion can be isolated by the it is adapted to suit the nature of such applistop-cocks, which are inserted at intervals, cations. without cutting off the supply from any large number of consumers.

Since the great fire in Wood-street, City, merchants are anxious enough to get rid of their steam-engines, and they welcome the hydraulic power because, while it works their cranes and lifts, it can be used on emergencies to force a jet of water from the ordinary supply up to any flames that may be discovered. Hence the company has found sufficient customers to induce it to lay a main up Wood-street and to erect a second pumping station in Philip-lane for future use. The mains, which at present measure in the aggregate seven or eight miles, are cast-iron pipes 6in. in diameter. They are in 9ft. lengths, and are tested to 2,500lb. per square inch at the works. The joints are turned and bored spigots and sockets, and are made tight with guttapercha rings, the necessary pressure being obtained by two 14in. bolts passing through lugs on each pipe. As each section is laid the water is admitted to test the joint; and after that, if they are tight, very little more trouble is experienced. Stop-valves are inserted every 400 or 500 yards, and by their aid the position of a leak can be located within that distance, after which it is easily found. Since the commencement of this year the quantity of water delivered has increased by 40 per cent., and as the charges are moderate the company has the promise of a very successful future before it In fact, the distribution of hydraulic power, first started in Hull, has gained a permanent footing in London, and will no doubt rapidly spread to the other busy cities of the kingdom.

TROUVE'S SURGEON'S ELECTRIC
LAMP.

HIN IS ON TONING FOR AMATEURS.* HE art of toning is one which the amateur is Tapt to give too little attention to. Excellence in all the manipulations connected with the production of a negative, even including the making of the plates, and, indeed, excellence in every operation in the production of the finished picture up to that of toning, is common enough with amateurs. Excellence in toning is not so common. "Nothing is easier than to tone, nothing more difficult than to tone well," had been said; and there certainly is much truth in the saying. By excellence in toning we mean not only the ability to get a good colour with pure whites and transparent shadows, but also the power of getting any tone we require, of course confining our requirements to the possibilities of the matter. The variation produced by varying the toning bath and manner of toning is not confined to the colour obtained only, but shows itself in the general quality of the print. We have before us two prints taken from the same negative, and printed on portions of the same sheet of paper. The colour of the tone cannot be said to be very different. It would be described as a warmish brown in each case. The difference in the general appearance is, however, great. The one is a clear, brilliant, and pleasing picture; the other, though it would scarcely be placed in the category of "mealy prints," is a flat, dirty, uninteresting looking object. Now these two prints were toned in the same bath. They were the result of experiments in the small details of the process merely, and show how much depends on these same.

give a print readily toned to a pleasing colour. It is difficult to see why it should be so, but it is evident is a great factor in the colour of silver prints that the gradation of density of the negative obtainable from it. We will get, as a rule, a better tone from a negative which might be described as "somewhat delicate but full of detail" than from the densest possible negative which is even a little under-exposed.

at another slowing down gradually to a measured pace, which gives the idea that they have not much to do. They are, in fact, self-regulating, and run at speeds which are automatically controlled by the work they are called upon to do, which is, briefly, to keep up the pressure to which the accumulator is loaded. During a busy hour, when cranes, capstans, Beginning at the beginning, and taking in sucand lifts are in full employ, the engines run as if cession the various small matters which we have they had work to do; but in the quieter hours found worthy of attention if we desire to get a their action appears to be spasmodic, though, in pleasing colour in our prints, we may take first of fact, it is entirely regulated by the demands all the quality of the negative. As is generally made upon them, and any movement in the known, the influence of this on the tone of the engine-room is an indication that the power finished print is very great, but wherein this instored in the accumulator is being drawn upon. fluence exists is apparently not quite fully underWithin a very recent period the system which stood. It is commonly said that a negative showhas been found to work so well at railway The devic patented by M. G. Trouvé, of Paris toned to a rich colour: but something more than HE device shown in the annexed illustration ing strong contrast will give a print which may be stations and docks has been extended through and is specially intended for the use of surgeons, this appears to be required. A negative with a certain parts of the City of London, and, judging though obviously it is applicable for other pur-contrast ever so great, if under-exposed, will not by the patronage it has received, it is likely to extend more and more until the hydraulic Poses. The principal object is to obviate the system completely eclipses the old-fashioned necessity of shifting the light with each movement of the patient, and the invention consists in the methods of working cranes, &c., in City ware.. houses. The system of distributing hydraulic power was first tried in Hull, and the success of the first venture naturally directed attention to the field open in London, and in 1882 a company was formed which obtained powers within a certain limited area to supply the City warehouses with the power which had been found so useful in the docks and the railway stations. During the present session of Parliament further powers have been acquired, and the district now conceded to this company extends on the north side of the Thames from the West India Docks to Vauxhall, with an average width of 1,200 yards, and on the south side from the Surrey Commercial Docks to Vauxhall Bridge, with an average width of 600 yards. The chief pumping station is situated near Blackfriars Bridge, on the Surrey arrangement of a frontal illuminating apparatus side of the river, and the company can take as for surgical purposes which may or may not be much as one million of gallons of water from the made adjustable about a centre, in order to project Thames every day-a quantity much beyond the rays in any direction desired to suit the their requirements at present, but which repre- movements of the patient while leaving the hands sents, supplied in driblets to meet an intermittent of the operator perfectly free. The entire demand, the enormous amount of 2,000 to 3,000 apparatus, which is shown in section, is attached horse-power. The water, as raised from the to a frontal plate a padded on the inside and Thames, is necessarily very muddy, but it is secured to the forehead by an elastic band B or passed first into settling tanks and subsequently by one or more springs like those of fencing through sponge filters until it is practically clear, masks, or by means of a spectacle frame resting

d

We do not intend at present to enter into the question of the manufacture or sensitising of the paper, because, as a rule, amateurs use readysensitised paper. We, therefore, pass on to the actual printing. It is an opinion commonly held that the longer, within limits, & priut remains exposed in the frame-that is to say, the poorer the light-at the time of printing, the better will be the tone. It is certainly the case that prints done in very brilliant sunshine, and, therefore, in a very short space of time, do not, as a a rule, tone as well as those which have taken louger to print; bat

we have not found the difference to be very great. The manner of keeping the paper both befor and after printing is a matter of importance, as we all know ready-sensitised paper turns brown from being kept. It may, however, turn in two totally different rays. It sometimes turns of the same colour that it would were it slightly exposed to light. This appears to be the effect of the action of pure air and damp, and does no harm so far as the colour obtainable by toning is concerned. There is, however, a very different discolouration which re

• From the Photographic News,