いし די 2 Castner process. Considerable quantities of metal were produced at these works, and most of it was of exceptional purity. As long as aluminium ruled above 3.00 dols. a pound, they were commercially successful; but inasmuch as it takes nearly three pounds of sodium to make one of aluminium, and the various other steps in the reduction are rather expensive, this process has not been able to compete commercially with the less costly electrical processes, and the Oldbury works are now devoted exclusively to the manufacture of metallic sodium, which finds profitable markets in Germany and elsewhere, being largely used in the chemical manufacture of anti-pyrene. -- Cowles process mainly by the fact that it operates exclusively or, at least, almost entirely-by utilising the chemical or electrolysing action of the current. This process is the invention of a young French electrical engineer named Paul L. T. Heroult, whose affiliations with the firm of Messrs. Henry Merle and Co., owning and operating the Deville Aluminium Works at Salindres, and his subsequent studies at the polytechnic schools at Paris and Switzerland, first directed his attention to the electrical reduction of aluminium. In 1886-7 he secured French, English, and other European patents, covering several other processes for the extraction of aluminium, silicon, boron, &c., from On April 2nd, 1889, Mr. Charles M. Hall, of their ores, both as pure metals and in the form of Oberlin, Ohio, secured patents for a process of re-alloys. On August 14th, 1888, he secured a United ducing pure aluminium. In this process alumina is States patent, No. 387,876, for the process of predissolved in a fluid bath composed of aluminium paring aluminium bronzes and their alloys, and it is fluoride and potassium fluoride, with, perhaps, an understood has pending in the Patent Office a series addition of lithium fluoride, this bath then being of applications covering other parts and features of electrolysed by means of an electric current con- his inventions. Though the Heroult processes have veyed to a carbon-lined furnace through an anode been very little discussed, or even described in print, of some non-carbonaceous material. In electro- and are, therefore, almost wholly unknown to the lysing this bath, the containing vessel is made to public, their commercial success abroad has been serve the purpose of the negative electrode. In far greater than has attended any other aluminium another patent, Mr. Hall claims the use of a bath process, and while those owning the American composed of alumina dissolved in compound patents seem as yet to have done little in fluorides of aluminium with alkaline earthy metals, the way of exploiting them, the success of a small and in still another patent, the use of a bath com- plant put into operation at Boonton, N.J., for posed of alumina dissolved in the fluorides of private demonstration purposes, in April 1890, has aluminium, calcium, and sodium; these materials been such as to give it rank among the prominent being obtained by melting together aluminium, aluminium processes. Having had exceptional fluoride, finor spar, and kyrolite. With this latter facilities for studying the workings of this plant bath a carbon anode can be used without the bath during the past four months, I might be pardoned being affected by its disintegration. -especially as so little is publicly known of it-for describing it at length, but as I particularly desire in this paper to direct your attention to the electrical apparatus used at Boonton, by way of illustrating the great power and value of the electric current in metallurgical operations, it will suffice here to say that the patents of this young engineer, having first been acquired by Swiss capitalists, were afterwards bought by the celebrated syndicate which, under the name of the Allegemeinen Electricitats Gisellschaft, of Berlin, substantially controls the entire electrical field in Germany. This syndicate, after carefully examining all other processes then known, invested ten millions of francs in the Heroult process, and are operating very extensive works, which obtain their power from the falls of the Rhine, at Schaffhausen. There they produce not only pure aluminium and all its alloys, but also alloys of silicon and other metals. Those works are supplied partly with dynamos of the type I wish especially to describe to you, and partly with dynamos of 600 electrical horse-power, a complete description of which I regret I am not able to place before you at this time, as they would interest you. These machines, weighing over 50 tons each, revolve horizontally; they have 24 pole-pieces with collectors over 12ft. in diameter, and were especially designed for economical work. The Hall group of patents is now controlled by the Pittsburgh Reduction Co., of Pittsburgh, Pa., which has had its metal on the market since March, 1889. The plant has a daily capacity for producing about 3001b. of metal, the selling price of which was 2-00dol. per pound until the early part of March last, when it was reduced to 100dol. per pound for commercially pure aluminium, of a guaranteed parity of 97 per cent. The reduction in price, considered in conjunction with the limited amount of pure metal produced, would appear to confirm the generally received impression that while the pure metal is specially adapted to the manufacture of articles of art and ornament, it is not displacing tin, platinum, silver, &c., to anything like the extent its admirers supposed it would. The fact is, aluminium as a pure metal is not destined largely to supplant other metals in the arts and manufactures; it is to its alloys that we must look to redeem the inflated reputation of the pure metal. The true value and use of aluminium seems to have been forecast by Deville, who predicted for it an intermediate position between the precious and baser metals, in which relation to manufactures he said it was destined to fill a long-felt and important want. He doubtless referred to the pure metal; but, curiously enough, his prediction applies with greater force to its alloys, which have been demonstrated by actual use and thorough tests to possess physical aud chemical properties that place them above all other alloys of copper, iron, and, in some instances, even of steel. The electric smelting process of the Messrs. Cowles, of Cleveland, Ohio, was the first to secure a commercial footing in this country. The furnaces used at the company's extensive works at Lockport are rectangular and oblong in shape, comparatively shallow, and are composed exteriorly of walls of firebrick or metal, lined with pulverised charcoal or other form of carbon or similar material, of electrical conductivity inferior to the ore to be smelted; this material being generally previously saturated with lime-water to increase its resistance to heat. At each end of these furnaces are inserted rods of carbon, which, passing through the walls and linings, are brought very nearly into contact within the body of the furnace, and, being conZected to suitable wires or cables coupled to the dynamo, constitute the positive and negative electrodes. The charge consists, ordinarily, of a mixture in different proportions) of an electrically resisting material-such as electric-light carbon-and the ore to be reduced; though (in cases where the ore itself has sufficient electric resistance) the carbon is sometimes dispensed with. The charge fills the furnace and presses against the sides and ends of the electrodes which project into the furnace. When a current of electricity is passed, the electrodes are so adjusted as to form an are, and the current then flows from the sides and ends of the electrodes through the broken resistance material, which, of course, becomes incandescent, and the intense heat developed by this incandescence reduces the ore, the metal flowing to the bottom of the crucible, and being subsequently tapped or dipped out when the charge is consumed. The gases liberated in the operation pass out hrough openings in the firebrick cover of the To give you a comprehensive idea of the method employed by Mr. Heroult in manufacturing aluminium and its alloys-and so far as electrical apparatus is concerned, there is little difference between his and the Cowles process-it will be best to describe the electrical plant and crucible separately. Unlike the Cowles process, Heroult's is a continuous process, the reduced metal being tapped from the bottom of the crucible while the machine is merely stopped or slowed down for a few minutes. The interior dimensions of the crucible vary with the ore to be reduced, and the size and character of the anode used. Ordinarily it has an interior depth of about 22in., and a clear space of 6in. between the walls and exterior surface of the anode. The electric current passes into the crucible through the suspended carbon anode, the vertical position of which is controlled by an attendant, who lowers it from time to time to preserve an approximately constant distance between the bottom of the anode and the surface of the molten bath in the crucible. The anode usually dips several inches into this molten bath, and in practice the intervening space between its bottom and the surface of the molten metal is kept at about an inch by the attendant, who by watching the needle of the ammeter is enabled to maintain the electrode in its proper relative position without difficulty. In order to get as perfect a contact as possible between the furnace and the cables leading therefrom back to the dynamo, the cables are firmly clamped to a large block of zinc, which projects from the rear of the furnace, and is kept cool by water circulating in pipes around which the zinc is cast. While, properly speaking, the crucible has no top, as a rule plates of carbon imbedded in dry alumina spread over the top of the crucible, are so adjusted as to fit close to the anode in order to retain most of the heat. The mouth of the crucible is formed of slabs of carbon built up funnel shape. The hearth or floor is pierced by a tap hole, which is kept closed by a plug of carbon or fireclay, and is opened from time to time to allow the molten metal to run into a carbon-lined ladle, from which it is cast into ingots. There are a few distinctive but not important differences between Heroult's method of making alloys and reducing pure metals simply. In making alloys, the base alloying metal is first melted in the crucible by the current, or molten metal is poured into the furnace, to form a liquid metallic cathode. This is usually simply and economically accomplished by throwing pieces of the metal-copper for instance-into the furnace, seating the anode upon them and passing the current. At first the current is very unsteady, arcs constantly forming between the copper and the anode, but when the copper is entirely melted (and it takes but a very few minutes to melt 200 or 300lb.) the ore to be reduced is added in sufficient quantities to form a bath, and fioats on top of the molten copper. The anode having been raised so as to leave a space of about an inch between its bottom and the molten copper, the current becomes steady, and the operation is established. Thereafter the ore is introduced in small quantities, at frequent and regular intervals, until the desired percentages of aluminium or silicon contained in the alloy have been secured. This percentage can be regulated entirely at will up to about 70 per cent. of reduced metal. No external heat is used, and the process is absolutely continuous at the will of the operatives, which are special features of the Heroult system. The passage of the electric current through the bath, serves not only to keep the copper in a fluid state and to melt the ore, but also electrolyses and decomposes the latter. It is a point of careful regulation in the Heroult processes to maintain only sufficient heat to keep the bath fluid, since any further expenditure is not only useless but lessens the output. The oxygen from the reduced metal combining with the carbon of which the anode is composed is burnt with the production of carbonic oxide gas, which escapes from the crucible around the sides of the anode and at the feed-hole. The product is withdrawn at intervals by tapping the bottom of the crucible as in ordinary smelting. The metal produced in the Heroult furnace is sold generally in ingot form, just as it is tapped, without re melting or being subjected to any purifying manipulation. It is always, however, very pure, sometimes dropping as low as 98 and, but generally running over 99 per cent. of absolute purity. This is largely due to the great care exercised in selecting raw materials. In making bronzes, the best Lake Superior copper is used, while the oxide from which the aluminium is reduced is an artificial product, manufactured in Prussia. The number of materials from which aluminium may be reduced by these processes is very large, but the strong influence exerted upon this metal by impurities reduces those ores commercially available in this country to corundum and beauxite, both of which At Boonton the bus wires are eight in number, are largely used in making low grade metal for four positive and four negative, each wire being treating iron and steel. Cryolite-natural or arti square, and having a cross-section of lin. They ficial-is another mineral that plays an important are, in fact, rolled copper bars, uninsulated, because part in the commercial production of pure aluthe low potential of the current requires no special minium, since it is the best flux for alumina, the insulation. An ammeter is placed in the main ore from which the metal is generally reduced. circuit by a simple arrangement, for the guidance There is to a certain extent a diversity of opinion of the workman who specially looks after the in regard to the value and properties of aluminium, crucible. The distance from the dynamo to the which is partly the natural sequence to the furnace (which is situated in another room) is only illusions and exaggerated opinion concerning 14ft. The four positive wires pass directly to the its commercial and practical value, resulting clutch which holds the anode, and the four negative from the romantic descriptions, speculations, wires pass from the ammeter back to the dynamo. and suggestions, with which our scientific and In the electrical apparatus the most important feature, of course, is the dynamo which generates the current. This machine was designed by Mr. C. E. L. Brown, of the Oerlikon Works, Zurich, especially for electro-metallurgical work, and is the only one of its kind in America. It weighs, complete, over 19 tons, and when driven at 220 revolutions generates a current of 35 volts and 3,500 ampères. It is a 6-pole machine, having an armature of the Gramme ring type, and the current is taken off commutators at either end by 72 brushes. The armature is 39in. in diameter, and the shaft (including its clutch) is 11ft. 7in. long. The commutators are each 19in. in diameter and 20in. long, each commutator containing 60 segments weighing 131b. apiece, or a total of 7801b. for the segments for one commutator alone. The core of the armature consists of a very large number of sheet-iron discs, clamped together in a frame of aluminiumbronze. About in. from the outside edge of the core 120 holes pass from one end to the other, through each of which passes a copper wire in. in diameter. These wires, which, of course, are thoroughly insulated from the core, form part of the winding. The remainder of the winding is composed of copper bars in. thick, 31in. long, and 24in. wide. trade literature have been filled ever since Deville's researches were published, and partly the result of impurities in the metal as ordinarily produced. For thirty-five years after Deville first produced it, aluminium, though much talked of, was but little seen outside of laboratories and lecture-rooms, except as we find it on the French and English markets manufactured into ornamental shapes. It is only since 1886 that it has been manufactured in sufficient quantities and at sufficiently low prices to permit practical metalworkers to test its properties on an adequate scale. The very unusual qualities which give it merit, and the great depreciation it undergoes when only slightly contaminated with foreign impurities, such as iron and silicon, together with the further fact that it has only been recently commercially produced of 99 per cent. purity, have had a tendency to prejudice this metal in the eyes of practical people. Mr. Green added some further explanations of USEFUL AND SCIENTIFIC NOTES. his method, and Mr. Waugh expressed his complete agreement with Mr. Cottam's suggestion, and undertook that, so far as possible, it should be adopted by the members of the section. Cleaning Sheets of Wrought Iron, &c.Wrought iron plates are pickled in hot dilute sulphuric acid in the ordinary way, commercial oil of vitriol diluted with 10 volumes of water being preferably used at a temperature of 200° F. The improvement consists in allowing the contents of the pickling tank when sufficiently concentrated to flow slowly through a long cooling channel and there deposit the greater part of the dissolved sulphate of iron, the mother liquor passing into a vessel from which it is continually pumped back into the pickling tank, vitriol and water being added till it is of the proper strength. The process is continuous after being fairly started. Cylindrical pickling tanks are used for cleaning wire.-E. P. PEYTON, Birmingham. A REMARKABLE railway accident is reported in the Indian Engineer. The Southern Mahratta mail train left Arsikere with two brakes, two composites, four third classes, one horse-box, and one postal van. Nearing the bridge at the twenty-sixth mile, and eighty-four miles from Bangalore, the driver observed a large bull suddenly make its appearance on the line 300 yards ahead of the train. He endeavoured to slacken speed, but before doing so the animal was run over, and its horns getting entangled in the bogie wheels of the engine, caused the engine and tender to be thrown off the rails. Six carriages behind the engine were completely capsized. The composites were completely overturned, the wheels being uppermost. The passengers escaped through the windows. Fortunately no one was fatally injured. The vehicles left on the rails were the horse-box, the postal van, and one brake. Cradina.-In 1880, in a communication to the French Academy of Science, M. Bouch ut reported that he had found the juice collected from the common fig tree (Ficus carica) to contain a powerful ferment capable of digesting albuminoid substances, thus confirming a belief of the ancients that the juice possesses digestive properties (Pharm. Jour. [3], xi., 250). This ferment is now the subject of a paper by Dr. Mussi, in which he reports its isolation and describes its properties (L'Orosi, Nov., p. 364). Juice collected from the fruit and branches of the fig was filtered to remove the serous portion from the insoluble, the latter repeatedly washed with water and the washings added to the filtrate. This liquid, which after repeated filtration was obtained limpid, was distinctly acid in reaction, and when placed in contact with moist fibrin digested it completely. It was evaporated to a small volume, again filtered, and treated with absolute alcohol, which threw down a plentiful white precipitate that dried, when exposed to the air, to a with water, swelled up and imparted a milky appeardark yellow amorphous mass. This, when treated ance to the liquid, but a clear filtrate from it, though it gave the reactions of vegetable albumen, had no digestive power. The residue, insoluble in water, dissolved readily upon the addition of a trace of acid or alkali, and the solution, placed in contact with moist fibrin, effected complete and true digestion. To the ferment thus isolated Dr. Mussi gives the name "cradina," from krade, the name given by the Greeks to the part of the fig with which they specially associated the digestive property. It contains nitrogen, and in the dry state it forms a friable, semi-transparent, dark yellow, amorphous mass, yielding an amber-yellow powder. In water it swells, but does not dissolve, though upon being shaken it imparts to the liquid a milky appearance. When dissolved by the aid of alkali or acid a concentrated solution is dark yellow, but becomes colourless upon being diluted. Cradina differs from pepsin in maintaining its digestive power in an alkaline liquor, and from papain or papayotin in being insoluble in water, not precipitated from solution by alcohol or lead acetate, and in its activity not being diminished in the presence of hydrochloric acid. In a neutral liquid it is devoid of digestive power, and it has no reaction upon starch.-Pharm. Journal. Mr. Sadler replied that though this might be the case with the larger formations, the small craters, or craterlets, were as a rule quite perfect. Mr. Green then replied, agreeing with Mr. Downing that the present mode of the moon's rotation was the consequence of previous tidal action; whilst in answer to Mr. Seabroke, he did not think that appearances pointed to a sinking of the mountainous districts as the cause of the features to which he had alluded. The President thought that the meeting would be interested to know that one of the chief assistants of one of the Continental observatories had been recently engaged in making a series of observations on the rotation period of Venus, and had come to the conclusion that the old estimate of De Vico's was correct, and that 23 hours was about the true value. The following papers were then announced, or partly read ::-On Stellar Distribution," by J. E. Gore; "A Photographed Meteor," by Dr. Max Wolf; "The Perseid Radiant," by W. H. S. Monck; "A Further Report of the Coloured Star Section," by W. S. Franks; and "Accuracy and Inaccuracy," by Edwin Holmes. The meeting was then made special for the consideration of some proposed alterations in the rules, for the purpose of altering the date of the annual meeting from June to October, and the revised rules as drafted by the Council were carried unanimously. Notting Hill-square. discussion was entitled "Inaudible Tones." It was The subject introduced for shown that tones may be inaudible from several causes, such as defect of wave-amplitude, from the vibrations being too rapid or not sufficiently rapid, wave-length being too great or too little, from the from their being overpowered by other tones which and from other causes. Many bodies vibrate in are sufficiently closely related to combine with them, such a manner as to produce tone-waves which are not of sufficiently great amplitude to excite the auditory nerve. Mr. Downing said that he hoped some members of the Jupiter section would turn their attention to the eclipses of the satellites. In a paper which he had the honour of communicating to the association some months ago, he had advocated the use of a photometer for these observations, and had pointed WESTERN MICROSCOPICAL CLUB. out the great advantages the photometric method possessed over the ordinary method of eye-esti-Tilt the met on Monday evening, 10 4.3., 11, HIS club the 4th inst., mation. He hoped, therefore, that, at all events some members of the section would adopt this method of observing the eclipses, and he ventured to assure them that they would thereby be doing good work for the advancement of their science. The President remarked that the tables at present available for the eclipses of Jupiter's satellites were rely on the Nautical Almanac predictions for an anything but accurate, and that if any one were to observation of the third or fourth satellite, he might very probably find that he was too late. He hoped that Mr. Downing's suggestion would be carried out, and that some of the members of the Jupiter section would undertake a series of photometric observations of the satellites during their eclipses. The work was not so showy, or perhaps they would have the satisfaction of knowing that so interesting, as some other departments; but they were doing work of permanent scientific value. By photometric observations of the phase of half brightness they could reduce the probable error of the time determination from 10 seconds to one. The President said that as there had been but a short time at the last meeting for remarks on Mr. Green's paper on the "Lunar Seas," the discussion might be renewed. Mr. Green replied that he was aware that some of the members did not agree with that portion of his paper which treated of tidal action as the force which produced these seas, and he greatly regretted the absence of Mr. E. W. Maunder through indisposition, as he had some remarks to make on the subject. Mr. Green then briefly restated his view, and said he would be grateful to any members present who would remark upon them. Mr. Downing said that he did not see how tidal influence could have formed the seas, as the earth and moon had ages ago arrived at a state of equilibrium, and the tidal influences which had brought this about could only have acted during that plastic state of the moon which existed in the remote past. Mr. Downing regretted that he was unable to agree with Mr. Green as to the effects which might be attributed to tidal action on the moon due to the earth's action. In former times, no doubt, when the moon's period of rotation differed considerably from its period of revolution and its mass was more as he could see, not of the unsymmetrical character plastic, tidal effects would be produced; but, so far required by Mr. Green's theory. Later on in the history of the earth-moon system, as the period of rotation of the moon approximated more and more closely to its period of revolution, such tidal action would become feebler and feebler, until, when the present state of things was reached, it would cease altogether, and a state of equilibrium, so far as this particular action was concerned, would be ar rived at. Mr. Seabroke remarked that there was no need to call in the influence of tidal action to account for the seas, as the higher surfaces of the moon may have subsided and the seas risen round the mountain forms, gradually destroying them. Mr. Elger objected to that portion of Mr. Green's argument which presumed that the seas were confined to the visible portion of the moon's surface, for at certain times of libration other seas came into view, as the Mare Humboltianum, and the portion of this sea which was visible might be but a small part of the whole. The President said that Mr. Green had laid great and reasonable stress on a feature which was obvious to them all-viz., that the formations on the circumferences of the lunar seas bore evident traces of having been broken down or worn away. There are numerous tones pro duced by vibrations which are too rapid to excite the sense of hearing. Illustrations of these may be drawn from the insect world, where we find some tones that from their frequence of vibration are very insect tones serve as a kind of test of the acuteness of close to the upper limit of audibility. Some of these show that some ears are very sensitive, while others our ears for detecting tones of this class; and they are totally deaf to the same tone-e.g., the chirrup of some grasshoppers. Near the lower limit of audibility there are many vibrations produced which length to be heard. Some of these may be felt, as are not rapid enough, and are of too great wavewhen we feel the slow vibrations of the big pipes excite in us a sensation akin to pain, as is someof a large organ before we hear its tones. Others times experienced when passing near a steam-boiler with a short funnel. Others, again, are slow enough to be followed by the eye, as may be seen in the puffs of smoke issuing from tall chimneys. Among the tones which are overpowered by other tones may be mentioned those which are produced times called upper partials, and serve by their com by means of musical instruments. These are some. binations with the fundamental in certain fixed and definite proportions to determine the characteristic quality of the tones peculiar to each particular instrument. These were illustrated, with some experiments, which may be very easily repeated. One of the digitals of a piano was held down by the left hand so as to raise the damper without striking the wire, a digital was pressed down with the right hand so leased, when the tone of the octave was heard to as to strike a wire one octave higher, and then reand other octaves, and in every case the wire freed be continued by the unstruck wire. This was repeated with the second octave, the third, the fourth, by the left hand continued the tone of the wire struck by the right. The discourse was further illustrated with various drawings and diagrams, among which were some very fine stereographs of non-planar vibrations drawn and kindly presented by Mr. A. Stroh. These elicited great admiration. A discussion ensued, in which Messrs. E. Bartlett, G. C. Karop, H. W. Maw, and A. W. Stokes took part. Manures.-The Agricultural Research Association, which, for 16 years past, has been carrying out special experiments on crops in Aberdeenshire, Sussex, and other counties under the direction of Prof. Jamieson, has just issued the reports of its proceedings during last year. The following are the manures recommended per acre for this year :For roots.-lcwt. steamed bone-flour, 2cwt. ground coprolite, 2cwt. slag, cwt. nitrate of soda, cwt. nitrate of potash, and 15 tons farmyard manur For grain crops.-cwt. steamed bone-flour, superphosphate, lcwt. nitrate of soda, and, nitrate of potash. te of For grass.-lewt. ni soda, fewt. nitrate of potash, cwt. superr sphate, and cwt. steamed bone-flour. SCIENTIFIC NEWS. THEP In a guide-book to the Nile and the principal monuments of the land of the Pharaohs, written by Mr. E. Wallis Budge, of the British Museum, the author rejects the notion that the pyramids were built for any astronomical purpose, contending that they were tombs, and nothing more. The late Mr. R. A. Proctor held the astrological theory to be the true explanation, and "astrology" at the time of the building of the Pyramids was practically astronomy, while Herr Nissen and Mr. Norman Lockyer show good reasons for thinking that ancient temples were oriented on an astronomical basis. The death is announced of Capt. Cecilio Pujazon, director of the marine observatory at San Fernando, near Cadiz, the naval observatory of Spain. Capt. Pujazon will be remembered by the Eclipse party of 1870 who went to Cadiz. He was in his fifty-seventh year. The fifteen selected candidates for election into the Royal Society on June 4, are Mr. William Anderson, M.I.Č.E., the author, amongst other works, of "The Conversion of Heat into Useful Work"; Prof. Fred. Orpen Bower, D.Sc., who holds the chair of botany in Glasgow University; Sir John Conroy, Bart., M.A., lecturer on Physics and Chemistry, Keble College, Oxford; Dr. Daniel J. Cunningham, professor of Anatomy, Dublin; Mr. G. Mercer Dawson, D.Sc., assistant director of the Geological Survey of Canada; Mr. Edwin Bailey Elliot, M.A. mathematician; Dr. Percy Faraday Frankland, B.Sc., chemist; Mr. Percy C. Gilchrist, the distinguished metallurgist; Dr. W. Dobinson Halliburton, B.Sc., assistant professor of physiology in University College, London; Mr. Oliver Heaviside, a distinguished student of electricity and magnetism, whose numerous papers have been found of great value; Mr. J. Edward Marr, M.A., geologist, Cambridge; Mr. Ludwig Mond, president of the Society of Chemical Industry; Mr. W. Napier Shaw, M.A., physicist; Prof. Silvanus P. Thompson, D.Sc., principal of the Finsbury Technical College; and Staff-Commander T. H. Tizard, a distinguished hydrographical surveyor and marine meteorologist. The present year is the centenary of Faraday's birth (he was born at Newington Butts, Sept. 22, 1791), and at the recent meeting of the Royal Institution, the following distinguished representatives of science were elected honorary members in commemoration: Profs. E. Becquerel, M. Berthelot, A. Cornu, E. Mascart, and L. Pasteur, of Paris; R. W. Bunsen, of Heidelberg; H. L. F. von Helmholtz, A. W. Hofmann, and R. Virchow, of Berlin; J. P. Cooke, of Cambridge, U.S.; J. D. Dana and J. W. Gibbs, of New Haven, U.S.; S. Newcomb, of Washington, U.S.; S. Cannizzaro and P. Tacchini, of Rome; J. Thomsen, of Copenhagen; T. R. Thalen, of Upsala; D. Mendeleef, of St. Petersburg; J. C. G. de Marignac, of Geneva; J. D. Van der Waals, of Amsterdam; and J. S. Stas, of Brussels. was occupied mainly with the president's address The report of the American Iron and Steel Mr. T. H. Cornish, of Penzance, has a note in LETTERS TO THE EDITOR. [We do not hold ourselves responsible for the opinions of our correspondents. The Editor respectfully requests that all communications should be drawn up as briefly as possible.] All communications should be addressed to the EDITOR of the ENGLISH MECHANIC, 332, Strand, W.O. All Cheques and Post-office Orders to be made payable to J. PASSMORE EDWARDS. • In order to facilitate reference, Correspondents, when speaking of any letter previously inserted, will oblige by entioning the number of the Letter, as well as the page on which it appears. much as he knows, but no more; and that not in this "I would have everyone write what he knows, and as 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." On March 18 last, 12,000 grey mullet-Montaigne's Essays. (Mugil capito) were captured, by means of a draw seine, by the fishermen of Sennen Cove, at Whit-ERRATUM-GREAT MEN AND SMALL sand Bay, Land's End. The fish were of fine CRITICS-THE PARIS OBSERVATORY quality, one being brought to Mr. Cornish which "PHYSICAL" FORCE HARVARD measured 2ft. in length, 1ft. 3in. in girth, and weighed 6lb. 10oz. On the 31st of the same PHOTOMETRY - ASTRONOMICAL TELESCOPE-TELESCOPIC ODDS AND month a Lowestoft mackerel driver, fishing some leagues south west of the Lizard, took 48,000 ENDS-CHANGE (?) IN THE LENGTH mackerel. No such catch of mackerel, for one OF THE DAY FIGURING LENS OPHTHALMIC INNER SATELLITE night's fishing, had ever been heard of before at Penzance, and what makes it more extraordinary, says Mr. Cornish, is that it should have taken OF MARS-GEOLOGICAL: THE DARTFORD place in March, when the catches usually average HEATH GRAVEL HIGH VACUA, AND STATES OF MATTERa few hundreds only. THE NATURE and PROPERTIES OF THE SUN DE OMNIBUS REBUS ASTRONOMICIS. The Pola, a vessel sent out by the Vienna western basin. Touching the question how far As a rule, the basin of the Black Sea is very At a recent meeting of the Paris Academy of Medicine a paper, by Dr. Berlioz, of Grenoble, was read, in which he described a new antiseptic, composed of 75 per cent. of naphtholate of sodium and 25 per cent. of naphthol and phenyl compounds. It is a white powder obtained by adding to fused beta-naphthol half its weight of caustic soda, and allowing the mixture to cool. It is soluble in three parts of water, and the solution is said to possess considerable antiseptic powers. The antiseptic properties of "microcidine, as it is called, while inferior to those of carbolic and boracic acids 10 and 20 times corrosive sublimate or naphthol, surpass those of respectively. that [32316.]-SEEING letter 32262 in print, I notice paragraph four (p. 202, col. 3) I seem to have written, in some wholly mysterious way, 3.75in. or 4in. aperture. I have, goodness knows, "8.5in. or 9in. aperture," where I meant to say suffered many things at the hands of the compositor but the decimal point makes me think that this wonderful blunder must have been what little children call "my very own." I In letter 31778 (Vol. LII. p. 247) in referring to wound up by saying: "But surely Prof. Hall Prof. Asaph Hall's admirable monograph on Saturn, never in his life saw the crape ring C so brilliant as it is depicted in the engravings before me." Now, it would appear that someone must have communicated this comment of mine to Prof. Hall; for in The Observatory for the current month, the famous been called to a criticism in the ENGLISH MECHANIC American astronomer writes: "My attention has of my pictures of Saturn, and as this criticism is correct, I wish to acknowledge it." I would invite particular attention to the attitude thus assumed by one of the most eminent astronomers living, towards a humble critic like myself; and contrast it with that taken by an English writer and propounder of a series of "magnificent theories" (dead and dying) towards men of far higher scientific position and ability than himself, when in justice to my own countryman, I am, of course, they have presumed to point out his blunders. But, constrained to admit that Prof. Hall is so really great a man, that he can afford to confess when he has made a slight mistake. A paper on the "Micro-organism of Diphtheria" was read recently at the Pathological Reading the Report of Admiral Mouchez on the Society of London by Dr. Albert Wilson, in condition of the Paris Observatory, presented to the which some of the views of Dr. Klein were com- impossible not to sympathise with him in the posiBoard on February 24th of the current year, it is bated. Dr. Wilson has shown that in ordinary tion in which he finds himself, or to avoid the excases of diphtheria a thin grey exudation pre-pression of a hope that his modest request for the cedes the membrane formation, and he believes establishment of a branch observatory away from that that exudation contains the causative micro- the disturbing atmospheric influences of a large organism. He considers that diphtheria is city may speedily be acceded to. When I first reprimarily a constitutional disease. member Paris (more than 30 years ago) the south Continent by the Canadian Pacific express, would seem that the inevitable growth of the city The run made across the North American view from the Observatory across the Boulevard St. Jacques was comparatively unimpeded; but it bringing passengers from the ss. Empress of has now so hemmed the observers in as to render a India landed at Vancouver, seems to have been a great deal of their astronomical work at once diffiremarkable one, as the entire distance (2,900 cult to perform and practically valueless when At the conversazione of the Royal Society last miles) was accomplished at a mean speed of it is performed. When Louis XIV. had the week the principal exhibits were connected with thirty-four miles an hour. Over the Western present building erected for J. D. Cassini, it was the science of electricity, Mr. Wimshurst's new Prairie the train is stated to have "made a record to all intents and purposes, in the country; but machine and Prof. Lodge's rotating mirror for of a mile a minute for hours," and, at parts, to now the City has stretched out her octopus-like arms and surrounded it. It is, by the bye, worthy analysing the electric spark attracting much have run at seventy to seventy-five miles an attention. The so-called colour photographs of hour. The Canadian express is to convey the of note that Perrault's original building, though termed by courtesy "L'Observatoire," has never M. Lippmann were also the subject of much con- mails from this country to China and Japan. from that day to this been utilised for the purpose versation. Mr. Crookes's tubes showing phos- The "rapid transit" commissioners of New for which it was erected, being (whatever its archiphorence in high vacua naturally attracted many York seem to be in some difficulty as to what is tectural merits) unfitted for the reception of astroof the visitors, while Mr. Shelford Bidwell's to be done for the congested traffic of the city. nomical instruments, which have consequently been demonstration of the effect of light on the elecfrom time to time installed in huts and pavilions in trical resistance of selenium was witnessed with various parts of the extensive grounds. Not only great interest by those who think that the houses, but it is proposed to bring the Sceaux Railthough, are these now hemmed in by streets and phenomenon when developed will yield important way within 164 yards of the Observatory, and what that means, let everyone who has ever observed the reflected image of a star in a trough of mercury results. The meeting of the Iron and Steel Institute The most likely systems to be adopted are the ENGLISH MECHANIC AND WORLD OF SCIENCE: No. 1364. Let imagine for himself. Admiral Mouchez has proposed to provide for the cost involved in the removal of the instruments, &c., and the housing them in a proper locality by the sale of part of the very considerable area of kitchen-garden and waste land surrounding the present building. But here the Academy has stepped in, and refused to sanction the disposal of this land; and as no funds are procurable from the Government, the unfortunate Director finds himself in an impasse. earnestly hope that his present appeal may be us favourably responded to. When we see how the Observatories at Brussels, Copenhagen, Rio Janeiro, and Washington have, one and all, had to be removed, we may thank our stars that Greenwich is not yet swallowed up in London. knows Charles II. did but few wise things indeed; Goodness but conspicuous among them may assuredly be reckoned the erection of our Royal Observatory on Flamsteed Hill. If I were asked to put an interpretation on the marvels attributed to Miss Mattie Lee Price by the San Fancisco Examiner (to which reference is made by "Dubitans" in letter 32279, on p. 205), I should be tempted to suppose that the editor of that journal, having succeeded in mystifying so competent an astronomer as the conductor of the Sidereal Messenger, had been making an essay in humbugging physiologists. Of course, the whole thing may be an ingenious advertisement of a clever exhibition of juggling or trickery, and may be put forth in the interest of some one's breeches-pocket. One frail woman does not pull against six strong men in America without money (and without Price). the head. Some time ago the little son of a clerical month of Phobos is only 7h. 39m. 15 1s. long, and to the character of a geological deposit in a locality The "variable-star observer" of whom Mr. T. N. Clapham speaks (in letter 32285) on p. 206 may be "of no mean order" in his own special sphere of astronomical work; but I gravely question his critical power, and demur to his authority when he talks of the Harvard Catalogue being "more attention to the subjects to which query 74356 I have not, I regret to say, devoted sufficient notable for quantity than quality" of the work. It (p. 212) has reference to offer an opinion of the has always impressed me as a monumental example slightest value upon them. I may say, though, of very remarkable accuracy, and as a priceless that I have no reasonable doubt that, by the guide to the observer in the measurement or esti- extremely ingenious and efficacious apparatus mation of star magnitudes. One would be curious employed by Crookes, vacua of almost inconto know the exact method employed by Mr. Clap-ceivable tenuity have been produced. Mr. Romanes ham's friend of comparing his stellar magnitudes is, of course, aware that, but for the trace of with those given in the Harvard "Annals." will not say that Prof. Pickering's gigantic work silver in an ordinary barometer, the so-called I mercurial vapour above the column of quickis infallibly correct in every single detail, but its "Torricellian Vacuum" would be a real one. Now, general accuracy is indisputable. Mr. Hails (query 74325, p. 212) apparently the exhausting tubes of a mercurial air-pump, no as long as mercury vapour is allowed to pass through thinks that an astronomical telescope can be as pressure lower than 025 millimètre is obtainable. easily made from merely verbal description as But if, in the duct leading from the pump to the a plain wooden box or a stool. the square leg of receiver, some non-volatile substance which absorbs Does he want a reflector or a re- the vapour of mercury is introduced, that vapour fractor-the Newtonian, Gregorian, Cassegrainian, will be arrested; as, by taking similar precautions, or Herschelian form-an achromatic or a nonachromatic instrument-or what? Considering the a very low pressure obtained. When Crookes (Phil. very small cost of this invaluable serial, and the Trans. 1878, CLXIX. p. 300) made his radiometer may aqueous or any other vapour be stopped, and iterated and reiterated directions for the construc- experiments, he absorbed the mercury vapour with tion of every known form of telescope that have sulphur; the appeared in your back volumes, I cannot but regard anhydride, and on the further side placed metallic your correspondent's request as-to put it mildly-copper to absorb the vapour of the sulphur in turn. watery vapour with phosphoric rather a cool one. tained With these precautions he alleged that he obi.e., 0·000002 of no reason whatever to doubt that he did so. pressure of only 00015 millimètre, In discussing the question of a radical change of an atmosphere, and I see state, we must be especially precise in the meaning we attach to that phrase. As an illustration, I would ask: Does water undergo a radical change of state in its passage, on the one hand into ice, and, on the other, into steam? Because, if not think that we can refuse to adopt the form of expression in question in speaking of Crookes's I do radiant matter. I can give no coherent explanation of Hittorf's experiment. On such a point, an opinion of "Sigma" would be worth fifty of mine. Mr. Fridy (query 74328, p. 212) may use a dark glass on his 2 in. telescope for observing the sun for some time, without any fear of cracking it, and, notably, if it be of a red colour. Castor, with a power of 200 on such an instrument, would show as two stars inclosed in a kind of figure of 8 of rings. In a Herculis, the comes should be well outside the principal ring. 10 is an ample power for a finder for such an instrument as his. Cross wires should be fixed in the focus of its eyepiece; which, for this purpose, must be of the Ramsden form. A regular equatorial mounting would be a costly luxury for a 2 in. achromatic; but the rudimentary form of it known as "Smeaton's block" would be found handy and convenient. No doubt, varying atmospheric conditions were answerable for your correspondent's varying view of Capella. In reply to query 74329, p. 212, undoubtedly the friction of the tides and the fall of meteoritic matter on the earth, must theoretically tend to lengthen the day; but then, as the earth loses heat by radiation and shrinks, such shrinkage must tend to shorten it. A so far unexplained amount of acceleration of the moon's mean motion has been supposed to indicate that the day is seemingly getting longer, so that our count of time would be getting too slow, and the moon would seem to be going faster. reduced the assumed acceleration from 12" to 8", Prof. Newcomb, however, has which renders it extremely doubtful if there is any discrepancy left to be accounted for. Certainly there is no proof whatever that the length of the day has changed one way or another by 01 second during the last 1,750 years. I am not, I am sorry to inform "Poor Glass Grinder" (query 74336, p. 212), a practical optician, and can only suggest the frequent use of a carefully-made template, applied in all directions over the lens to be figured to a true sphere, as a means of indicating where it requires grinding down on. Were I Mr. Bruce (query 74342, p. 212), I would institute a most rigid inquiry as to whether the a assume 80, MAY 15, 1891. 2, 3, and even 400,000 miles above the stupendously descent hydrogen gas rushing up to a height of 1, heated photosphere of the sun? Prior to again to procure, read, mark, learn, and inwardly digest rushing into print, may I counsel your correspondent Prof. Young's beautiful book on "The Sun," published in the "International Scientific Series." Any shilling book on astronomy will correct his peculiar notions as to the cause of the Seasons. of questions, several of which are obviously unanswerable. Who, in the existing state of human Mr. Wilkinson (query 74389, p. 234) puts a string but little in colour; or, in the cases of unequal mately equal components of a double star differ knowledge, can possibly say why the approxithe spectrum-i.e.. towards the violet (not topairs, the tint of the smaller star lies higher up wards the red)? With regard to No. 2, Neptune has scarcely been observed through a sufficient arc for the perturbing effect of an exterior planet ceptible, not only in the case of Neptune, but that of Uranus too. In fact, 14 years ago Prof. Todd did lay parent; but some day such an effect may be per(assuming it to exist) to have become very apdown graphically the difference between the computed and observed places of Uranus, and-after allowing for the perturbations produced by Neptune-came to the conclusion that there was an undiscovered planet whose longitude was (then) about 170°. and wholly failed to find it. But he made an exhaustive search for this hypothetical body with the great Washington telescope, Asteroid hunters, as to a deal of protracted watching to be thus detected, a class, recognise the objects of which they are in trans-Neptunian plauet would require a great unless it presented search by their motion, which is fairly rapid. A 3. Stars scintillate because their light comes humidity, and hence its rays must travel with very perceptible disc. strata of various temperatures, densities, and different velocities. Collecting these rays then in a us through an atmosphere composed of telescope, the result of their reaching us in different phases will be apparent in the alternate brightening and darkening of the image. This only happens, though, when rays issue from a point. The rays from a large planetary disc would issue from such innumerable points as to neutralise each other. My intelligibly described phenomena of his vertical querist can apply this explanation to the not-toospectrum. law of gravitation only. know, suppose binary systems to be acted on by the better read the article, "Nebular Hypothesis," in 4. We must, as far as we at present Nichol's Cyclopædia of the Physical Sciences. 6. 5. Mr. Wilkinson had A nebula must, of course, be hot enough to emit light; but not "intensely hot" like our own sun the heavens. Finally, I would humbly venture to ask, How parallel strata of air, dense or rare, can why the nebulæ aggregate in the way they do in or a star. No human being knows moon, immediately after she has risen, for himself. up a brown-paper tube, and look through it at the "act like a lens"? I wish that Mr. W. would roll about her being "magnified." Did he ever see a He would at once see what nonsense it is to talk mite of a thing when passing over head, and balloon come down in the distance? Because I appeared an enormous object as it neared the have; and can assure him that it looked quite a earth, albeit it was actually nearer under the former condition of things than under the latter. A Fellow of the Royal Astronomical Society. THE SHIFTING RADIANT OF THE PERSEIDS. interested in this subject will do well to peruse a short paper printed on p. 407 of the Monthly Notices [32317.]- THOSE of your readers who are Meteor Showers," and who has latterly been infor April, 1891. Prof. Kleiber, of the Imperial vestigating the orbits of the 918 showers given in in the press on "The Determination of Orbits of "Observatory, St. Petersburg, who has a book now my paper in the Monthly Notices for May, 1890, says: "I may add, as a first preliminary result of my computation, that it confirms the shifting of the radiant of the Perseids during the six weeks of the A glance at the orbits corresponding to all the radiants related by Mr. Denning to the Perseid activity of the shower, as observed by Mr. Denning. shower will show their identity at once." I grieve to be obliged to assure in this matter, and Prof. Kleiber's result, in com- MIGHT BE aware of the remarks of Sir D. Salomons, but they are not put forward as anything more than estimates, and require a great deal of proof even in their bald nature. Nothing is said, it should be noted, as to the cost of the gas-engine and the dynamo and the lamps-items which must be reckoned in the balance-sheet. Mr. A. Percy Smith says that, "if you set up an engine and dynamo of your own, it will not cost more than 4d. per unit, making the light but little more costly than gas." It is well known that gas does not give the amount of illumination it ought to do if potential energy were always the equivalent, but if that gas-engine can give double the amount of light that gas will when burned in the ordinary way, I ask, where can the fact be seen and realised? The simple question is, What is the price of the electric light compared with gas, both supplied by companies in the usual way? Incans. and who generally study the moon and planets) THERAPEUTIC MAGNETISM. [32322.]-I HAVE been very much interested in the valuable letters of Gerard Smith on Therapeutic Electricity." May I ask the same gentleman to favour us with his observations on the uses of magnetism for the same purpose? We are LUNAR ATMOSPHERE AND hearing and reading a good deal about the wonderful TEMPERATURE. curative effects of electric belts-has anyone any[32319].-IN letter 32125, which appeared on the thing to say about the action of magnetic belts on 6th of March, I gave reasons for believing that the animal tissues? It is well known that these do not mean temperature of the moon was about the same screen magnets, but allow the lines of magnetic as the mean temperature of the earth. These force through them. Do these lines in their passage reasons were not controverted at the time, and Mr. affect, for good or evil, the animal tissues through Peal (32299) now merely asks me to remember which they pass? Do they quicken or retard the "that in speculating in regard to lunar phenomena circulation of the blood? Do they soothe or stimuwe must not apply too rigidly our terrestrial late the action of the nerves? From observations analogies." What, then, are we to do? Accept coming recently under my notice, I am inclined to the analogies when they on our own side, and dis- think they are as capable of doing both as regard them when they are against us? This is effectually as electric current passing through those too often done, but it should be evident that no tissues. I have had the opportunity of examining conclusion can ever be arrived at, if both parties a number of patients attending the magnetic to a discussion act on this convenient principle. establishment of Mr. James Cole, 250, CaledonianCuriously enough, Mr. Peal's only argument is road, N., and have been placed in communication drawn from a supposed terrestrial analogy. He with many who have been cured or relieved by his says that the earth's atmosphere acts like the glass course of magnetic treatment. Their condition of a hothouse, permitting the sun's heat to enter, before treatment does not admit of a doubt respectbut preventing its return again by radiation. The ing the serious nature of their ailments. Loss of illustration is apparently apt, but there is really no power in limbs by paralysis, joints fixed and painful analogy between the atmosphere and the glass. with rheumatism, cripples, carried into the Mr. Peal must remember that there are other cool-establishment. Whilst there, they sit in contact ing agencies besides radiation, and one of them-an with permanent steel magnets, or within the inimportant one-is atmospheric convection. The fluence of magnetic batteries. Whilst at home atmosphere, instead of keeping the earth warm, they wear belts and other appliances, made up of actually removes a portion of the heat derived from permanent magnets. After a few attendances at the sun as soon as it is received by the earth. The the establishment, they are relieved from pain. A air in contact with the earth gets heated and rises healthier condition of the body ensues, and in the atmosphere, taking the heat with it. We improvement goes on, until, in a few months, shall now understand the work that is done by the the patients crutches, then these glass of a hothouse. It imprisons the heated air of are given up, and, finally, the formerly the hothouse and prevents it from cooling the stiff joints become supple and flexible, and the interior by convection. Instead of playing the weak limbs regain their strength. It all seems part of an atmosphere, as Mr. Peal supposes, it wonderful to me. I cannot understand the action actually prevents the atmosphere from doing its of magnetism applied in this way; but I cannot cooling work. close my senses of observation to what I see and hear. One lady residing at Greenwich has regained the use of her leg after being 27 years a cripple. A stonemason stricken with paralysis on one side has now regained the use of his arm and leg, and can do a good day's work. A young girl condemned by the surgeons to lose her foot is now able to skip about as well as ever she was. Another young girl, now attending the establishment, was so paralysed as to be unable to feed herself; can now dress herself and sew, and hopes soon to get well enough to get about on crutches. come on it is merely desired to obtain sharply-defined dots, whereas in planetary work it is desirable to obtain detail of their surfaces. One of the difficulties in this branch is, that a planet not only revolves in its orbit, but also rotates on its axis, and, therefore, to increase the length of exposure does not seem likely that detail can be obtained. Up to the present our knowledge of the surfaces of the planets and the number of their attendant satellites has been solely obtained by eye observations. Additional discoveries have been added from time to time by every additional increase in optical power. Theoretically, new discoveries would continue to be made if we were able to continue to increase telescopic power. But in this matter there are also difficulties at present insurmountable. We are not able to produce object-glasses of very large dimensions which possess good defining quality (the largest o.g. at present being 3ft. diameter), and in the case of giant reflectors, they are exceedingly heavy and cumbersome, besides the labour and difficulty of resilvering, and the necessity of readjusting them afterwards. Moreover, an observer using this type of instrument is compelled to be situated at the mouth of the tube (if he is desirous of obtaining the best view of the image the mirror produces), which is not usually convenient. Considering the diffi culties which appear to retard the progress of our knowledge in respect of the solar system, I merely suggest a style of reflector which would be very powerful and inexpensive in mounting, and probably would add new discoveries towards the advancement of astronomical science. The usual massive tube and heavy counter-balances would not be required, neither a huge rotating dome or a powerful driving clock. The principle is very simple, and perhaps may be understood by the rough sketch, Fig. 1, in which a is the mirror mounted on trunnions, which would only require a small dome of about 6ft. high to cover it; b is the observing house (placed in the meridian) in which is firmly fixed the frame e for carrying the eyepieces. The rays of light from, say, the moon, which strike against the mirror, could be reflected toward the eyepiece in the observing house, and the image magnified in the usual manner. The eyepiece could be adapted to move in any desired position to suit the observer by the aid of two screws, marked d and e, and when once the mirror is adjusted, there would be no necessity for the observer to change his position. Of course, the driving and the adjustments of this type of instrument would be half the amount required in the ordinary style of telescope, and would be specially adapted for planetary work, but its range could be extended by placing another observing house on the north or both sides of the meridian. An instrument of this kind could easily have great focal length, and probably by dispensing altogether with the tube, it might materially add towards steady THE COST OF ELECTRIC LIGHTING. definition. Having read of a tender being given for a reflector as large as 8ft. in diameter with the [32320.]-YOUR correspondents, whilst endeavourusual style of mounting, I am inclined to think ing to make out a good case for the electric light, that larger ones might be produced. With regard neither do nor can question my statement that 1d. to the operation of resilvering, that could be per Board of Trade unit is practically equivalent to more easily accomplished than 1s. per 1,000c.ft. for coal gas for lighting, and that the present method, as the mirror need never be removed Sd. per unit for electric light is equal to 8s. per when once it has been placed on the trunnions. 1,000c.ft. for gas. I did not question the fact that All that would be required is to turn the gas used in a gas-engine will give more light when face of the mirror towards the ground, and the power is converted into electricity than when by removing a pin for holding the foot of the burnt in ordinary burners; but the cost of plant, polar axis, the mirror could then be lowered suf- attendance, renewals of lamps, and wear and tear ficiently to clean the trunnion arms, and the silver- must also be considered. I may be a special pleader ing bath placed underneath on an adjustable table. I in favour of coal-gas, but it is quite certain that if do not think it unreasonable to say that with a I could get a better light with less trouble and grand instrument of this description we could be expense I should choose the best without favour. enabled to view the moon at a distance of about 15 their own against all comers for other purposes than not more clever than the leading prestidigitateurs of The gas companies are quite in a position to hold miles. For instance, say a mirror of 12ft. in diameter having a focus of 130ft., and by applying lighting, and in spite of all opposition their work and profits are steadily increasing. Mr. Peal says that he never assumed that the I do not pretend to understand what Mr. Peal an eyepiece of, we should then have a power of 15,600, which calculated on the mean distance of the moon (less the semidiameters of the earth and moon), would bring its surface to our view as close as just mentioned. Moderate size instruments might become very general, as the cost probably would be smaller than the reflectors of the present day, and many amateurs (possessing limited means, Ja. Ha. Thos. Fletcher. I could mention dozens of such cases. This comes as a revelation to me, and I wonder at the remedy not being better known. Can Mr. Gerard Smith throw any light on the subject? G. E. Bonney. HYPNOTISM AND INDIAN JUGGLERY. [32323.]-I HAVE seen a good deal of Indian jugglery and conjuring. It differs in no way from that common elsewhere, except that it is usually performed in the open air-sometimes in a tent. Nearly all the published accounts I have read are exaggerated, and evidently written by persons who knew nothing even of the rudiments of the art. Consequently, influenced by the love of the marvellous, and being completely duped, they attribute what they do not comprehend to mystical powers beyond the realm of ordinary facts and experience. That these Indian conjurers are extremely dexterous, and that their tricks are well and neatly executed, cannot be denied; but they certainly are Europe. [32321.]-My object in asking the question as to the "cost" of electric lighting was to ascertain exactly how the figures came out, say, in the case of a Regent-street tradesman who had adopted the electric light in place of gas. I am perfectly well Persons in the hypnotic state can be made, as we all know, to imagine that they see all kinds of objects which have no existence in reality. Consequently the hypnotic state has been called in to explain some of the phenomena said to occur at the séances of certain mediums. But, assuming this to have some bearing in such a case, the condition of affairs is very different to that of the spectators under consideration. In the first case, those pre |