is engines or motors not exceeding 5H.P. effective but perfectly safe for use in small workshops or dwelling-houses. Steam-engines will be excluded unless they offer great advantages. Particulars can be obtained from the Executive Committee of the Exhibition, Palermo, or from the Consul-General for Italy in this country, 31, Old Jewry, E.C. The Thomson electric welding process is to be taken in hand by a company in America having a capital of £100,000 for the manufacture of shells for the army and navy. The experiments with liquid fuel for locomotive use are stated to be successful on the Great Eastern Railway, twelve locomotives being now fitted with Mr. Holden's apparatus, besides some stationary boilers. USEFUL AND SCIENTIFIC NOTES. THE Parliamentary return of the owners of two and more on-licensed houses, recently issued at the instance of Mr. Summers, M.P., shows that 172 members of the House of Lords own 1,539 licensed drinkshops; 19 dukes hold 321, 12 marquises hold 106,74 earls hold 645, seven viscounts hold 45, one bishop holds two, and 59 barons 420. LETTERS TO THE EDITOR. [We do not hold ourselves responsible for the opinions of All Cheques and Post-office Orders to be made payable u J. PASSMORE EDWARDS. •In order to facilitate reference, Correspondents, when speaking of any letter previously inserted, will oblige by mentioning the number of the Letter, as well as the page on which it appears. "I would have everyone write what he knows, and as much as he knows, but no more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that as to other things, knows no more than what everybody does, and yet, to keep a clutter with this little pittance of his, will undertake to write the whole body of physicks, a vice from whence great inconveniences derive their original." -Montaigne's Essays. THE PERSEID RADIANT. [32176.]-MR. BOOTH's results from Plasmann's observations are of considerable interest, especially as the August shower of 1888 was little observed in this country owing to the cloudy weather. They undoubtedly tend to show that the Perseid radiant shifts in an easterly direction for a few days before AN alleged photographic novelty is now on view (and probably after) the maximum. But there are, at the Literary and Philosophic Club, Berkeley-I think, several reasons for not laying too much square, Bristol. It is a coloured photographic stress on them. In the first place, Mr. Booth print, said to have been taken directly from nega- notices that they give a diffused, not an accurate, tives, the process adopted having been successfully radiant. In the second place, Mr. Denning and carried out by Mr. F. Bligh Bond, architect, of that Mr. Booth both deduced a principal radiant at city, who is Hon. Sectretary of the Bristol and 42° 57° (or 42° 57°) from a considerable West of England Amateur Photographic Associa- number of meteors on the night of August 8th, tion. The photograph is of cabinet size, and is a 1888, for which night Plasmann's radiant is at view of Land's End. It is a chromo-collotype, and 41° 52°. In the third place none of Plasmann's is printed in blue, carmine, and yellow from a set radiants are very close to the cometary radiant with of three negatives. As intimated, the print is pro- which this shower has been identified. If we supduced directly from negatives, which it is claimed pose the limits of error to be wide enough to have undergone no retouching or manipulation reconcile Plasmann's observations with those of Mr. beyond the chemical development. The principle Denning and Mr. Booth, on the one hand, and involved is the selection of the colours of nature in with the cometary radiant on the other, they are the negative, and their recombination in the print, also wide enough to render it doubtful whether which is said to be permanent.-British Journal of there was any shifting. Photography. Illuminating Power of Coal-Gas.-As the temperature at which coal is distilled is increased, the yield of gas from a given weight of coal increases; but with the increase of volume there is a marked decrease in the illuminating value of the gas evolved. Mr. Lewis T. Wright, Journal of the Chemical Society, found that when four portions of the same coal were distilled at temperatures ranging from a dull red heat to the highest temperature attainable in a retort, he got the following results as to yield and illuminating power:-Temperature 1, dull red, gas per ton 8,250 cubic feet, illuminating power 205, total candles per ton 33,950; 2, hotter, gas per ton 9,693 cubic feet, power 17-8, candles per ton 34,510; 3, hotter, gas per ton 10,821 cubic feet, power 16.7; candles per ton 36,140; 4, bright orange, gas per ton 12,006 cubic feet, power 15-6, candles per ton 37,460. I hope some of your mathematical readers will compute the amount of shifting which stray members of the cometary shower ought to exhibit if met with three or four days before or after the maximum. Dublin, March 20. W. H. S. Monck. THE MOON'S ALBEDO-TIDAL FRIC- [32177.]-I AM much obliged to "F.R.A.S." for his kindly correction, but I meant what I saidnamely, that, according to Sir John Herschel, the moon's disc, taken as a whole, reflects more light than the rather light coloured rock of Table Mountain, and I italicised the word " 99 more to show that I meant it. It would have been better probably if I had added a sentence or two to explain why I meant it. If "F.R.A.S." will kindly turn to my first article on "The Moon as shown in the Lick Telescope," published in Knowledge for Oct. Scents and Perfumes.-In 1889, 44,608 gallons 1889, p. 215, he will find that I there quote Sir of perfumed spirits, chiefly eau de Cologne, valued John Herschel's words as he gives them; and I at £87,629, and paying a duty of 10s. 6d. per gallon, add that Sir John Herschel states "that at the were imported into England. Of essential and time of the observation, the sun and moon were perfumed oils there were 1,078,2771b., valued at nearly at equal altitudes." Shortly after writing £192,340; and of perfumery and articles used that article, I was looking at the frontispiece of therein, 1,367,8471b., valued at £139,746. The Sir John Herschels's volume of "Results of lavender water distilled at home, the otto of roses, Astronomical Observations made at the Cape of musk, Tonquin bean, patchouli, and other per- Good Hope," and noticed the very considerable fumes imported, bring up the total to £500,000 altitude of the " grey perpendicular facade" of sterling. Of orange-flower water, jasmine and Table Mountain as seen from Sir J. Herschel's neroli oils, citronelle and lemon-grass oils, a great observing station, as it is shown in the picture; deal are received. There are about 10,000 acres It struck me that if the sun and moon were at nearly under Andropogon nardus grass in Ceylon, and over equal altitudes at the time of the observation, the 5,500,000oz. of the citronelle oil made from it are moon, when observed, could not have been full. shipped. Lemon-grass oil is obtained from other Zöllner has shown that the full moon reflects more species, Andropogon citratus and A. schonanthus. light, area for area, than the partial phases, because About 9,000oz. are shipped from Ceylon. Geranium when the moon is full we see none of the shadows oil, which is much used to adulterate otto of roses, cast by rising ground, whereas at all other times is distilled in Algeria to the extent of 12,000lb. the whiteness of the moon is affected by the Otto of roses is chiefly produced in Turkey and admixture of a certain proportion of black shadows. India. At Kezanlik and its neighbourhood about Consequently, it seems to me that Sir John Her80,000oz. are made. At Adrianople the yield of an schel's observation shows that the moon's disc average crop of roses is from 600,000drm. to reflects more light than the rock of Table Moun825,000drm. It requires about 3,000lb. of rose tain. I agree with "F.R.A.S." that terrestrial leaves to produce an ounce of otto of roses. The volcanoes seen from the moon would appear of a Turkish oil is that most found in our market; but dark colour. I have not seen many volcanoes, but much of the rose oil which England consumes comes have been upon Etna and Vesuvius, and was much also from India, it being largely distilled in the struck with the black desolation of the lava streams North-West Provinces and the Punjab. From of Etna. Vesuvius is not quite so dark. The lava India there was exported last year 12,128 gallons of streams which have flowed from it differ considerdifferent essential oils, valued at £20.277. Of this ably in colour, and the cone and Monte Somma quantity, 3,000 gallons came to the United King- have a brownish look, but the general appearance dom, 1,000 gallons were sent to France, and nearly is dark. The extinct volcanoes of central France all the rest went to the east coast of Africa, Arabia, would have a reddish look if there were no grass and Egypt. But if we use a great deal of per-upon them, but would appear considerably darker fumery, we also export perfumed waters, distillates, and articles of perfumery, to the value of about £110,000 a year. than light sandstone. Although the bright band along the moon's limb indicates that the lunar mountain tops are white, it is evident that only a small portion of the moon can be covered with clean snow, for Zöllner's estimate of the moon's albedo shows that the moon as a whole reflects less than a quarter of the light that would be reflected by clean snow; consequently, if a quarter of the moon's surface were covered with clean snow, the remainder of the moon's surface would be absolutely black, and though the maria are relatively very black as compared with the broken mountainous regions, they are very far from being black. The contrast.of brightness is best seen when you dim the light of the moon with a dark wedge, or better still, with two Nicols which introduce no colour. As to the colour of the moon, which is a very different thing from its brightness, I have frequently momentarily mistaken the moon's disc as seen in the daytime for a small white cloud; and I have mistaken clouds seen upon the horizon for snow mountains, and have only subsequently distinguished the clouds from the mountains by their rounder forms. There is no prevailing colour, such as red or green, about the lunar landscape. The tints, whatever they are, so entirely neutralise one another, that the general summation effect is whiteness, and we do not see any decided tints when the lunar details are enlarged in the telescope. This is very different from the general effect of colour given by a terrestrial landscape as seen from a high mountain, and personally I feel it difficult to believe that we see the real colour of the lunar rocks even between the snow-covered areas. If I may throw out a speculation, it seems to me possible that the uniform colour may be caused by the accumulation of the meteoric débris of ages, which has not been covered up on the surface of the dead lunar world, as it would rapidly be here by worm-casts and vegetable growths as well as rains. If the moon has a thin atmosphere, such as I have shown reason to suppose, the outer surfaces of falling meteoric bodies would be vitrified, as they are during their fall here. But a larger proportion of meteoric matter would reach the surface without being driven into gas and falling in precipitates, as it chiefly does here; for the lunar atmosphere has its strata of increasing density (owing to the smaller lunar gravity) six times as thick as our own, so that the velocity of meteoric particles would be more gradually checked than here, and they would lose a larger proportion of their heat by radiation. I quite concur with "F.R.A.S." in what he says of Sir Robert Ball's delightful little book, "Time and Tide," but I think that Sir Robert's statement, quoted by "F.R.A.S.," that there can be no loss of moment of momentum" in a binary system, but only an exchange of axial moment of rotation of the primary into moment of revolution of the satellite, is not true. There must always be a certain proportion of loss due to tidal friction. In the case of the earth, the motion of the tidal wash, which is converted into heat and radiated into space, is derived from the earth's moment of rotation, and is altogether lost to the system. I will make one more attempt with the dogmatic "Ja. Ha.," but must leave him to his theories if he does not acknowledge his error this time. "Ja. Ha." says that whether the sides of a vessel are in-sloping or not, every inch of surface bears a pressure due to the height of the column of liquid above it. So far, he is quite right; and it follows that the pressure on the base of a cone-shaped vessel of water with in-sloping sides is just equal to the pressure on a similar-sized base of a cylindrical vessel filled to a similar height. But the downward pressure exerted by the base of each vessel on a table or scale, must be equal to the weight of the water plus the weight of the vessel. Let us suppose that the two vessels when empty are of equal weight. Then the conical vessel full of water will clearly weigh less than the cylindrical vessel when full. Therefore the pressure of the water on the base of the cone-shaped vessel must be partly counteracted by the upward pressure of the water on its in-sloping sides. As to "Ja. Ha.'s" last paragraph. He must not comfort himself that I now agree with him. It is clear that he does not understand the meaning of the word "vertical," which can only be defined with reference to the direction in which gravity acts. Consequently, the vertical direction at the Paris Observatory is not parallel to the vertical direction at Greenwich, and a stratum about a planet which is vertically over another has a larger and larger area the higher we go up. A. Cowper Ranyard. CLOUDS ON MOON. [32178.]-"F.R.A.S." (letter 32159) says will I explain in what I conceive the particles, supposed to be ejected with an inrush of gas, be suspended above the surface. Naturally, in the gas by which they were carried up, and which I presume would again gradually return to the interior as the force was expended, without there is a slight layer of gas present on the surface, when it would be gradually diffused into the surrounding gas, the particles gradually subsiding to the surface. He will, no doubt, remember the long discussion some years ago about the Crater Linné, the supposed altered The opinion about the absence of water or the moon's surface is principally that there is comparatively little signs of erosion, the action of which is to fill up hollows and level surfaces. If the moon had undergone the conditions of atmosphere and its accompanying effects for a few thousands of years, should we not be justified in supposing that many surface markings now visible would have been obliterated and hidden under the soil caused by erosion and vegetable growth, and other causes which combine to produce the smoothing effect? In fact, the presumptive evidence seems to point to the moon being in the state at which it would arrive when the molten matter had cooled down to its zero of temperature, that its only internal heat is that due to superincumbent pressure, below which I infer it can never sink. I never had the presumption to suppose that I could contribute to the knowledge possessed by your correspondent, whose fortnightly letters are looked forward to by so many of your readers with pleasure, and we must all hope that his store of varied knowledge will long be at the disposal of your readers, which is so freely given to those who have not the time or opportunity for otherwise obtaining it. His question as to whether the supposed bodies circling round the sun would be planets? I suppose they would, although perhaps inconvenient as places of abode from the long season of cold and comparative short one of great heat, which conditions would be inimical to vegetable or animal life. I think we cannot in fairness suppose that all these observations are the effects of imagination, or mistaking round sunspots for transiting bodies. S. Broughton. SATELLITES OF SATURN, 1891. [32179.]-I SEND you diagram of Saturn's satellites, plotted from Mr. Marth's Ephemerides, as given in the Monthly Notices of the R.A.S. for November last. It will be noticed that the apparent orbital motion of Japetus appears to be diametrically opposite to that of Titan, Rhea, Dione, Tethys, Enceladus, and Mimas. This is not really the case, but is the result of projecting the two classes of orbits upon paper, or what is the same, on the background of the sky as seen in an inverting telescope. 17th to July 16th, the small circles representing its apparent position for every third day. The dots represent the five inner satellites at greatest western elongation. H. P. Slade, F.R.A.S., 16, Westcott-street, Hull, March 16th. OPTICAL SCIENCE. [32180.]-I TRUST "Orderic Vital" (letter 32143) will, on reconsideration, decide upon sending his notes on "Prisms." I should like to ask "Orderic Vital's" opinion of the following as an improvement, or otherwise, on the usual construction of the spectroscope. My idea is that if for one of the ordinary 60° prisms (in an instrument containing several of these) were substituted two half-prisms placed at either end of the train, with their shorter faces, of course, directed to collimating lens and .g., a considerable increase of light and therefore efficiency-might be obtained with the same amount of dispersion, and possibly likewise permit the use of prisms having larger refracting angles, thereby giving increased dispersion without that excessive loss of light which attends their employment in the usual manner. Can "Orderic Vital" say why the angle of 60° is so generally adopted in the construction of prisms for spectroscopes? I know of no special virtue attaching to this particular angle other than the symmetrical shape it imparts to the prism. Have experiments proved that it is really the most suitable angle for the purpose, and more effective generally than angles of any other degree, greater or less? If so, it appears to me a somewhat curious coincidence. W. T. N. mixture of boiled-oil and turpentine. The balloon must then be blown up with bellows, and hung up several days till dry. A second coat of varnish will make it airtight, or even a third coating may be given, while the balloon is blown up with air. The net is made of thin string, and has fifteen meshes long and seven meshes deep, made on a board 8in. across. This net must inclose the balloon at each end, or it will escape. Twelve strings from the net support a wooden rod 34ft. long and in. square. On the top of this rod is a frame made of pieces of wood in. square, and covered with paper. The rod is hung by the ends of the frame, and below the rod at each end are two wire brackets, in one of which a propeller-fan 10in. to 12in. diameter revolves. The fan has a wire hook in its axis, from which is stretched a piece of double elastic to the bracket at the opposite end. The elastic should be in. or so square, and 5ft. long before being doubled. By twisting the indiarubber 300 to 400 revolutions, the balloon will travel at a rate of two to three miles an hour for a considerable distance. A car to hold about 40z. ballast should be made to slide about on the wooden frame and balance the balloon, which may be kept on a level by allowing 6ft. or 7ft. of thick cotton-cord to trail on the floor. It is, perhaps, not generally known that Blanchard first used the propeller in 1784; but owing to the size of his balloon, the speed was too little to be noticed by the public, and it was then given up. A balloon of large size can, however, be driven by engine power at the speed of 16 to 20 miles per hour, which is above the average speed of the wind. J. Sutcliffe. PERMANENT VACUUM AIR-SHIP. [32182.]-MR. WILLOUGHBY is only two centuries behind time in his idea, which is that of the Jesuit Francis Lana (1670), who proposed to raise a AIR-SHIP MODEL. [32181.]-AFTER reading the project of a steel vacuum air-ship lately described, many of your readers would conclude that a working model is advisable. As I believe the matter of air naviga-vessel by means of metal balls, strong enough, tion is one of general interest, I send instructions how to make a working model air-ship. Anyone with ordinary mechanical skill and care can construct the model; but the size given is the smallest that an amateur can attempt with any chance of success. which equals the capacity of 35c.ft., and with The balloon must be 6ft. long and 3ft. diam., -༢༤ 36. 27- The following device will dispel the apparent illusion, if we bear in mind that upper side means the south side, the lower, the north, &c., as in diagram:-Take a small hoop, and, supposing it to represent the orbit of Titan, divide it by two strings into quadrants. Hold it at arm's length in front of the eye, and as near as possible to a white wall; tilt the hoop until its upper surface forms, by perspective, an elongated ellipse. Then supposing Titan to be moving in the direction of watch-hands around this ellipse, project its orbital motion mentally upon the white background-it will appear normal. Now tilt the hoop so that the eye rests upon its under surface, and go through the same process, and the motion in the projected orbit will appear abnormal. Although really in the direction of watch-hands, it looks on the wall as if contrary. This latter position of the hoop represents the orbit of Japetus. In Titan's case (as well as that of all the inner Manchester gas, which is heavier than most places, satellites) the superior conjunction, or furthest dist- it has a lifting power of one pound. It is made ance from the eye of satellite, takes place at upper with 18 sheets best tissue paper. They are pasted three culmination, whereas in the case of Japetus, the together first to form six pieces 90in. long by 20in. superior conjunction takes place at lower cul-wide. The gores of the balloon are cut in the form mination, and this fact accounts for the apparent and with the dimensions given in the drawing A B. illusion. They must then be held against a window and all the large pinholes pasted up with paper. The gores can then be pasted up, both ends having a paper cap fixed on when the paper is dry, and also a funnel mouth in the centre, by which the balloon is inflated with gas. The greatest care is required, so that no holes are left in the joinings. When the paper is quite dry, the gores are varnished lightly with a A scale agrees with the declination scale. ve been reduced by multiplying it by of the planet's declination. This kes the major axis of the orbit of it half a second in time longer than it been. Referring to diagram, it will be Le place of Japetus is given from March when exhausted, to resist the pressure of the external air, but at the same time so thin as, in the same circumstances to be lighter than their bulk of air. In a theoretical point of view, the idea is unexceptionable; but as a fact it is impossible, as was proved by Leibnitz. ORGANETTES.-VII. Sm. [32183.]-IN justice to myself, I must first refer to Fig. 15, page 55. I sent up a carefully-drawn tracing, sufficiently large to show the details clearly. It has been reduced to about half-size, and converted into a mere broken-lined ghost of the original, and I am informed (too late) that tracings do not reproduce well by the process employed. It has been already mentioned that the first application of the perforated bands to automatic instruments was in the case of a pipe organ. This was in 1848 or 1849 (the patent was taken out in the former year, but the specification is now out of print and unobtainable), and I remember in 1851 seeing the instrument in a room at the Society of Arts, in John-street, Adelphi. Whether this is still there, or whether it is no longer in existence, I do not know, but possibly some other correspondent can tell us. In this instrument the tune-band passed between the wind-chest and the openings leading to the pipes, so that it served as the actual valve. I was informed by an organ builder (now dead) that a great deal of money was spent on the experiment to try and cure the droning effect, which was so disagreeable in its tone, but that the attempt was a failure, and the scheme was abandoned by the patentee. Curiously enough, the moving the paper intermittently does not seem to have been tried, or, in all probability, success would have been attained. When the tune-band moved slowly, the wind was, of course, admitted to and shut off from the pipes gradually, so that prompt speech and correct tones were alike impossible; but by moving the perforation in the tune-band sharply into coincidence with the he p 2 ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1357. air passages, leaving it at rest for the required time, and then sharply moving it forward again to close the passages, this difficulty would have vanished. The 32-note organette referred to in my first letter has its tune-band thus moved forward step by step, but, so far as the tune is concerned, the effect is just the same as if the motion was continuous, the intermittent movement necessarily keeping time with the rhythm of the melody. Even a waltz sounds quite smooth and regular in its succession of notes." The step-by-step motion in this organette is ingeniously contrived so as to accelerate the movement of the tune-band when a short note has to be Bounded. The ratchet-wheel has two clicks connected with the bellows-handle; but only one of these is ordinarily in action. When, however, a short note is required-i.e., shorter than would be given by the smallest perforation - a spring is allowed to come up through a supplementary peforation in the tune-band, and thus allow the second click to also act on the ratchet-wheel, thereby advancing the tune-band two steps instead of one. Of course, by having these supplementary perforations the whole length of the tune-band, the speed is doubled throughout, and such is the case with one or two of the bands that I have. I w the same principle applied to another very small organette, and I imagine something like it is employed in the little toy accordionettes" one sees advertised. If the correspondent who recently asked about automatic pipe organs would like to experiment on something simpler than the pneumatic actions now to be described, I think what I have endeavoured to explain may perhaps serve him as a foundation to work upon, though many of the actual details would need careful consideration. Coming now to the application of the pneumatic action to automatic pipe organs, I show in Fig. 17 a simple arrangement that I have devised and am applying experimentally to an ordinary four-stop ELECTRO-BIOLOGY. [32185.]-MR. GERRARD SMITH (letter 32165), in answer to Myrddin Gwyllt, leaves a doubt whether cause of the chemical action in the body, stomach, The pneumatic action is controlled by the tune- the current (electric I suppose) is the result or the band by means of the levers L, and the valves conto hear the opinion of Dr. Büchner on this very nected to them, and the working is as follows:-- liver, &c. Perhaps it may interest him and others The two valves V and V' are on the same stem, so that when the upper one V is open, the lower one interesting subject. In his "Force and Matter," V' is closed, and this is their normal position as page 187, he says: "Electricity, a force the manishown in the Fig. There is now a free communica- festations of which were hitherto only observed in tion through the channel K between the wind- the inorganic world, plays, according to modern chest and the inside of the bellows B, which, there-investigations, a very essential part in the physiofore, are expanded under the action of the pallet logical functions of the nervous system. Electric spring R in the lower wind-chest. As soon, how- currents constantly surround the nerves when at ever, as the nose-end of the lever L enters a per- rest. These currents cease, or become weaker, foration in the tune-band T B, the tail end of the whenever the nerve is excited to activity. The lever, by means of its connecting wire, pushes the nerves, therefore, are not the conductors, but double valve downwards, thereby closing V and generators of electricity. This generation ceases opening V. The air contained in the bellows then with the activity of the nerves-that is, with sensaescapes through V'. The bellows are immediately tion or the exertion of will. Psychical activity accollapsed by the unbalanced pressure in their cordingly was, by some, defined as latent electricity, wind-chest, and the pallet P is pushed open by and sleep as a relaxed function of the electrical the sticker. When the perforation has passed, the nerves. Experimental inquiry may, perhaps, lead reverse movement of the valves closes the outlet, us to more intimate knowledge of psychical and the bellows B are again expanded and the functions." pallet itself shut, by the pressure of the spring R. Though shown in a line in Fig. 17, the levers and valves are to be considered as brought much closer together than the pallets (so as to get a narrower tune-band), the communication channels K being radiated to suit the difference in the widths. For the same reason I am putting the valves in a double row, like the pallets in the organette described in my fourth letter, page 548. Obviously a very similar arrangement could be adapted to either a harmonium or American organ instead of the pipe organ. By way of exemplifying the automatic principle in its most complete form, I give the Fig. 18 taken from the patent specification of November last, which is the most recent of any relating to these instruments. There are the pressure bellows AB for supplying the pipe-chest, and the exhaust bellows CD for creating the vacuum in the pneumatic-action chest P. This part is almost a repetition of the action shown in Figs. 12 and 13 of Letter V., except that the pallet, instead of opening the passage from the reed, opens either an escape-valve, O, or a passage, O,, communicating with the second set of bellows marked O. Thus, as a first step, we have the bellows O expanding and contracting under the control of the tune-bands. In thus opening and closing, these bellows O, by means of a sticker, open and close the two alternating valves M, and M, In conclusion I may, perhaps, mention the most seance had a most unwelcome recent manifestations of "spiritualists" in London by the sudden at a "dark" dénouement, by one of the sceptically inclined F. W. H. visitors exposing their "tricks," turning on of an electric light concealed in a scarf-pin. COST OF ELECTRIC LIGHTING. [32186.]-"INCANS," in his letter (32157, p. 58), opens up a very interesting subject-the cost of electric lighting. The following figures illustrating the history thus far of the London Electric Supply supply of electricity in existence. The authorised Corporation are very instructive, as showing the operations of the largest scheme for the public capital of the company is 1 millions sterling, of which more than £700,000 has been paid up. The total expenditure since the formation of the present company is £650,000. The total expenditure in round numbers has been for mains, £121,000; plant at Deptford station, £102,000; transformers, £33,000; meters, £4,800. If we now turn to the revenue account, we find it exhibits a remarkable equilibrium, the expenses balancing the receipts to within £19 14s. 3d. The total receipts for 1890 (that is, up to November 15th, when they ceased to supply current on account of a serious fire at the Grosvenor converting station) ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1357. being £28,704 9s. 11d. The charge, I believe, is In conclusion, I shall try to give "working" N. Brackenridge. THE COST OF ELECTRIC LIGHTING. Park," I would say-Write again and again. You CIRCULAR CUTTERS. MARCH 27, 1891. HINTS FOR EXPERIMENTALISTS. [32194.]-I NOW describe a method that may be used for the isolation of those portions of a negative which comprise half-tones within any given limited compass of shade or density. [32187.]-ON p. 72 "Bjorn" asks whether In fact, in our several cases we are both right, but length from the others, as described in letter 31993. Using ordinary dry plates instead of sensitised [32192.]-I CAN see now why "F. C." and myself tives, having each received exposure of a different through not knowing each other's thoughts each parts of the picture; the others show more of it in differed in our ideas as to serrating cutter blanks. paper, make a series of, say, five transparent posi thought the other wrong. Still, my plan would answer quite as well for round-faced as for hollow-posed positive, which will show every detail, make One of these is developable only in the very darkest faced cutters. graduated proportion. From the most fully exof the positives, in inverse order of their densities. each containing a different proportion of the halfsimilarly another series of graduated negatives, The positive and negative shades in each compound tone. Now superpose each such negative upon one let the exposures given be slightly different from such as would lead to this effect, and we shall see, sent a uniform degree of opacity in every part. But image might be so balanced as that it should pretion with such of the half-tones in the original by transmitted light, zones of a lighter shade in our negative as are comprised within a limited range of compounded plate, which zones correspond in posi density. Finally, using a camera with reversing mirror, and giving a short exposure, the lighter photographed, and will furnish the desired resultzones in these several compound plates can be "Incans" has "fallen into the error of taking the expenditure of 95 per cent. for the result attained." If "Bjorn" had endeavoured to answer my question-a pertinent one, I think-as to the actual cost of electric lighting, he would not have fallen into his peculiar blunder. The "duty" of a serrating round-faced cutters, by all means let us dynamo is its capacity compared with the power have it. I go on the principle that one cannot When you have tried the plan you mention for applied to drive its armature. It is easy to see that learn too much, and often find that one man's ideas (taking Dr. Gerald Molloy's statements second-lead up to fresh ones on my own part. hand from one who shows that he does not understand them) Dr. Molloy, who knows what he is if working with a vertical cutter frame the simplest talking about, did not mean the "duty" of a way is certainly as you propose, and would also Regarding the serrating of the worm-gear cutter, dynamo. I mention this matter because lately be the correct one if an additional" slide were and to add a hint that it is just as well to under- spindle; but if the top slide of the rest were placed there has been too much of this kind of blundering, used for the vertical slide when using the drill stand a question before attempting to answer it. vertical, you do away with the horizontal slide, and it is only in the special lathe mentioned that you can avail yourself of the saddle for the horizontal OLD OAK VARNISH. Incans. [32188.]-A VILLAGE joiner who often does jobwork for me, accidentally discovered that Brunswick black, well thinned with turpentine, thing. He was asked to renew an oak chair by a an excellent customer, who brought him a bottle of the above by mistake for gold size, and having mixed it with the turpentine, he only then found out that he had hit on a nice colour. I have had two new solid oak chairs and a side table in pale, natural wood, with transparent varnish, transformed by this workman into antique brown, matching an old oak chest, near which the above furniture stands. I give the process:-Remove the old varnish by the application of caustic potash in hot solution till the wood becomes quite bare and smooth. become quite dry, then with a brush apply a very Let the work thin mixture of turpentine and Brunswick black, taking care to let it soak well into the grain of the wood. After this first coating is hard, go over it again with a varnish made rather darker by adding a little more Brunswick black. Lay it on very smoothly. If the colour, when dry, be thought too brown, it can easily be altered by washing with pure turpentine till you get the desired tint. LATHE MATTERS. Eos. [32189.]-WILL C. C. Ellison kindly say what glue he uses in joining say a piece of hard wood on a boxwood chuck? I find great diffiulty in softening and removing my work. I use fish-glue dissolved in acetic acid, and generally manage to spoil the appearance of my work, using hot water before I can succeed in getting the pieces apart. Can pure aluminum be turned with the ordinary tools, and where can it be got? Will any electrician kindly furnish details of small electric drilling machine? Lastly, I should be very much obliged to the gentleman who wrote not long ago about new spherical slide-rest, if he will give us drawings of it. a C. F. D. [32190.]-IN reply to Mr. F. Carre's query about the "take-up find on examining the woodcuts relating to the of the "geared drill spindle," I article that there is a small error-viz., the loose cone should not butt against the slight shoulder on spindle, but have about fin. to set up. The shoulder on spindle must therefore be turned down in. longer to allow cone sliding up as wear takes place. The "set-up" is regulated by the tail screw, as "F. C." surmises. The error is mine, in making the drawings. I notice, in my article on Lathe Attachments in last issue, that the sketches of "slotting bar" have been reduced, and that the bracketed portions, showing cutting-tool and binding-screw, are still marked "full size," as I drew them, but which, as printed, they are not. cutters and screw alike are made from in. steel The wire, threaded in screw plate, to give them additional holding power in so small a shank. The holes in holder are all tapped same thread. The cutters have each a flat filed on one side or both sides, if necessary, on which the binding-screw pinches, and thus keeps them in position. To prevent further mistakes, I will in future append a proportional scale to my drawings, so that they may be, even if reduced, scaled. Old Correspondent, M. LATHE ATTACHMENTS-THE GEARED DRILL-SPINDLE. 191.]-IF Mr. F. Carre will read what I did etter 32134, p. 34), he will, I think, acknowhat I did not say I "think little of the which pleased" F. Carre "so much." An Old Subscriber," as well as "Earlswood traverse. speaking, wheels with small pitch, such as tangent on valuable space, as the subject now on hand is are in use, or which have been suggested, we IS MANGANESE NECESSARY IN CELLS effect of compound colours. Of these white light OF THE LECLANCHE TYPE? sceptical as to the recuperative power of cells using has acted wherever all of the colours in the series places where this has occurred, we can make from described, having each a certain degree of intensity, Approximately only, we may say that white light each one of our series of five or six detailed posi have overlapped one another. tions a very light print upon sensitive gelatina paper, the short exposures being somewhat varied To pick out the in each case in an inverse ratio to the relative pro portion in pure white light of the rays to which the prints are to be rolled up in solid black ink, and successively adjusted by register marks in a frame respective plates were sensitive. These gelatine before a fixed camera, and so photographed, with equal drop-shutter exposures, on one single sensitive plate. The resulting negative will define, in its most transparent parts, picture in which we have a strong white-or nearly white-light, and it only remains to give this those portions of our printing surface. negative a very short exposure upon the sensitised sensitised gelatine in the last operation, and by negative, made in the ordinary manner upon were such as is needed for printing on the ordinary sensitised gelatine, could directly; for instance, by suppressing only one ha It may be remarked that a positive transparency of the spectrum at a time, by means of the arrange be got in the camer ment of prisms described in letter 32072. I orthochromatic plate negative would exhibit no deposit of silver on the parts representing either the suppressed colour black. I believe that after some further explan used, the resultin more practicable than at first sight, and th tion this photochromic printing process will appe ultimately, some of the principles and metho concerned will be found in a wide field of com mercial application. Apropos of M. Lippmann's heliochromy, I wi o record the following method by which I have ought it just possible that the colour of a thin Im could be photographically regulated. Take a late showing very slight relief, say an electrotype fa Daguerreotype; smear it with, say, albumen, nd press it upon a perfectly flat glass plate, as the similar experiment with a pair of glass lates described in Brewster's "Optics," or a film I bichromatised organic matter on a glass plate uld be so exposed and developed as to exhibit an ccessively small degree of relief, and could be milarly pressed upon a second sheet. It would so be possible to regulate what Brewster calls the colours of thick films" by photographic means. I should like the experience of electrical readers your armature. The addition of 15in. would bring up diameter of core to 5.625in., or a circumference of 17in., which would leave plenty of room for the 152 turns per layer, and still enable you to leave supports for armature. In all dynamos, and especially in small ones, the air space absorbs a large percentage of the total ampère turns, as you will see by the following:-Ampère turns for air x 1660, space z dd, where Again = a [73848.]-Screw-Cutting.-Consider that while the work makes 13 revolutions, the lead-screw must make two revolutions. I understand by "tail pinion of 12" you mean a pinion either on the lathe spindle or revolving in unison with it. In which case, multiply its number of teeth (12) by the threads you wish to cut (13), and divide the product (156) by the pitch of lead screw (2). The quotient (78) will be the number of teeth in gear on lead-screw. F. D. H. America. [73861.]-American Organ.-Take the advice of those who have told you not to alter your Alexandre harmonium. The idea of altering har lines of force (Z) through armatnre monium to American organ is both absurd and im Ex 106 Sx Ne' total E.M.F. in volts. S = revolutions per minute. Ne= number of turns on armature. Ampère-turns for magnets =T to whether benefit would result from the closure of commutators, which are made of ridisable_material, in an atmosphere devoid of ygen. I do not see that much difficulty would where E = and in the way of doing this, and I suppose that, by any means the destructive effect of sparking uld be modified, important benefits might result. would be more practicable, for instance, to conrt alternating into direct currents, by means of alternating current-motor in the same, or a anch of the same, circuit, and provided with itable connections. A. D. REPLIES TO QUERIES. In their answers, Correspondents are respect. My requested to mention, in each instance, the title d number of the query asked. Where a = length in inches of magnetic circuit. a = area in square inches. Z = lines of force passing. the same manner. Now the number of lines of force passing through the magnets is always more than that passing through the armature, on account of magnetic leakage, which varies with the design of the The ampère-turns for the armature are found in machine; 30 per cent. is probably sufficient to add. Unfortunately, I have been away from home for some time, and cannot lay my hands on the particulars previously given. I must, [73371.]-Stoves.-It is no new thing to cause therefore, ask "Slow Speed" to wait another rfect combustion in stoves, or, in fact, any fire-week, when I hope to be able to send him an ice, furnace, &c., at least not to me. I exhibited example worked out from the particulars he has ay and model at the recent "Work" Exhibition given. I have used Kapp lines. J. W. W. B. utilising waste heat in the form of hot flue [73717.]-Machine for Enlarging Drawses for the consumption of sewer gas and the ings.-An apparatus of the kind suggested was, if tilation of sewers, the same thing to be applied recollect, patented and described in the "E. M.," house stoves for the consumption of vitiated air but whether it is "used in England" I cannot say. the room where fire was burning. By my It was a sheet of rubber expanded in all directions ention you can cause perfect combustion in by means of screws in the framework. naces, at the same time consume sewer gas, ich is so injurious to health, and in the case of ves or open fireplaces you consume the vitiated from the ceiling line, and by providing proper ets you have perfect ventilation, at the same e perfect combustion. I may say I was awarded t prize-viz., silver medal, money prize, and t-class certificate. The essay, &c., is protected ler the Exhibition Act of 1883. Please to see rertisement in Wanted. RUSSELL. [73722.] Laboratory. I have a "fume closet"-it is only a "miniature affair" as the "Gondolier" has it. It is about 3ft. square, with a cone-shaped top made of cardboard. The pipes leading into a neighbouring chimney breast are 4in. diam., and made of brown paper. This serves admirably; the joining places have a band about 1 in. wide pasted round them. All acid fumes pass off, and the piping is not in any way affected by them. W. HALL. [73723.]-Oil Hardener.-Why does " Querist" wish to harden "olive" oil in particular? What purpose can it serve? O. M. [73739.]-Tube Drawing.-The ferrules must be knocked out with a long rod, properly cupped, so as to touch the ferrules. When putting the tubes in they must be expanded with the usual form of tools. The query is rather incomprehensible, for any one intrusted with such work should surely know how to do it, as a steam-boiler is not a thing to be played with. J. T. R. 73523.] Why an "Unmitigated Nuisce P-In reply to "Earlswood Park," I said hile ago-not from theory, but as the result of ravating experience-that in addition to the st perfect taper fit, a "set-screw" is necessary en cutting intermittent patterns, especially with engine and large moulding drills. Carlswood Park" incidentally replies that a setw is not only "useless," but "an unmitigated sance." Having used a set-screw for many rs without the slightest inconvenience, I was cious to know, that I might be prepared to meet, enever my turn came to encounter, the serious ections conveyed to my mind by the above exssion; hence I simply asked "Why?" And "motive" (clear enough) was to obtain infortion. I am relieved to be informed that the d of the screw may get in the way-a congency which I had foreseen. To spoil a piece of ry worth £2 or £3, and throw away perhaps a ek's work for want of a set-screw is an unmiticed piece of folly, which no one will perpetrate [73844.] Pattern-Making.-The following want of warning if I can help it. But it is a will fulfil the requirements of the querist. It is e country," and those will do it who so choose, quick setting-five to ten minutes-and easily t not more than once, I fancy; so let me worked. Take rosin and beeswax, in such proterate the advice I ventured to offer to my portions so that when set it can be pared with ther-amateur: Use a set-screw without fail for an ordinary carpenter's chisel. If too brittle, add intermittent cutting. It is only like crossing a more wax, but only sufficient to render it easily que: very little trouble or nuisance, but some-pared. Foreign matter, such as whiting, does not des of greatest importance. C. C. ELLISON. harden it, but simply makes it more economical. 73712.1-Type-writer Ribbons.-The inks nerally used with type-writers are pigments, und up in water, with the addition of a little cerine. It should be simply rubbed on the bon with a bit of flannel, but the querist should lly try for himself, as a few trials would teach n more than an acre of writing. Some use simple ck ink, thickened with a solution of sugar. [73744.]-Model Launch Boiler.-Anything within the dimensions given will do. Use any thickness of copper that you can work, and as to rivets, anything you can get. There are no definite rules for these model boilers, for they must of necessity be out of all proportion to any useful boiler in existence. W. M. T. M. For rounding corners, deposit a sufficient quantity in the angle and use a piece of round iron or steel bent at an angle and polished; heat it and run it backwards and forwards on the stopping till it takes the form. This iron must not be too hot, or the stopping will not retain its form. Any surplus will be thrown up as a ridge outside the sweep, and can be easily pared off. If the querist will advertise his address, I will send him a small quantity of In large patterns this filling in is made of wood the proper consistency and a sample of the work. strips planed out to fit in the angle, and termed "hollows." The Americans advertise a flexible 73644.]-Strength of Field.-As your core is n. diameter, not counting the cogs, the circumferce is rather over 16in., and the diameter of No. 14 th two coverings of cotton being lin., you should ily get the 456 turns in three layers. You will d I recommended you to turn off the cogs, and rease the diameter of the core by means of fine n wire, not lumps on any account. Your coga nding up in., the following would, I think, be ir best plan. Three layers No. 14 would require out 35in., so you might increase the core by metallic hollow, as per sketch, but I have never in., and still have the same finished diameter for used it. practicable. "Organon" (p. 77) asserts that octave couplers cannot be added to harmoniums unless the action is lowered or the keys raised. If he or any other reader cares to advertise his address in the "E. M.," I will fully explain (free of charge) how octave couplers can be added to harmoniums. I know for a certainty that it can be done, as I have now in my possession a harmonium to which it has recently been successfully applied. Mr. Slatter's advice is bad and impracticable, and I warn "Gimal" against such impracticable ideas. Stubbins. J. SCHOFIELD. [73861.]-American Organ.-As "Gimal" says, there is not much variety in the tone of the two sets of reeds; but if he must persist in his determination to spoil a good instrument, I will not help him. from one who asks such questions!), he will spoil If he attempts to voice the 8ft. reeds (fancy that, the "percussion" effect; and as to what "Elève" said, please note the words a "very indifferent harmonium "-a phrase he, of all people, never applied to one of Alexandre's instruments. No, "Gimal," if you want an American organ, make one or buy one: don't spoil a good harmonium by attempting to alter it. In the case of a very indifferent harmonium," the advice might be different; but it is always better to sell such instruments, and make an A.O. on its proper lines. "Gimal" may take it as absolutely true that he cannot improve his harmonium by any possible alteration of the kind suggested. 66 ORGANON. [73881.]-Lathe Crank-Shaft.-I have noticed that the hooks are only alternately in contact with the shaft-viz., right hand at bottom, left hand at top: would that influence the matter. The lathe has been running nine years, and has never given trouble before. The hooks are of malleable castiron, with a round bearing surface in. wide. Wrought-iron or steel hooks are seldom used in these parts. Materniestr. 3, Dresden. A. F. SHAKESPEAR. [73899.]-Wiring Bells and Telephones.— The battery wire from pushes 1 and 2 should not be connected to earth at right-hand top corner, but fall to pushes Nos. 3, 4, 5 only. ELECTRIC. [73930.]-Lathe Matters.-The tool has not enough clearance. Materniestr. 3, Dresden. A. F. SHAKESPEAR. say that more than half the general turners in shops [73930.]-Lathe Matters.-I unhesitatingly do not know the best way to do this and the best shape tool to do it with. I submit rough sketch of A B round-nose turning tool, B, which I consider a good many strides in front of that in common use, which I also sketch (Fig. A). I also submit Fig. C as round-nose planer, which cannot be beaten. Tool A may in a very strong lathe and machine do its work apparently well, but B will even then do it a lot better; while either used in lathes and machines of the pattern and in the condition which the vast majority are found will want no comparison or any trouble in choosing from. SHOPMATE. [73935.]-Aron Meter.-This instrument is specially designed for central lighting stations as a recorder of the electricity consumed at the various points on the circuit. It is largely used in the various German central lighting stations. With the illustration, which is lettered to correspond with the following description, a fair idea of the instrument can be obtained. Two pendulms, A1, A,, control two distinct clockwork gears. A, is a standard, and oscillates at a regular speed. The second, A,, has a permanent magnet, B, instead of a weight, and is variable in speed. The variation is 712470 A |