The English Mechanic AND WORLD OF SCIENCE AND ART. FRIDAY, MARCH 29, 1872. ARTICLES. a mark. His conjunction with the Moon at Venus is a morning star, but is indifferently 1st 0h. Am. 23 proaching a circular she is, altogether, from ASTRONOMICAL NOTES FOR APRIL. BY A FELLOW OF THE ROYAL ASTRONOMICAL SOCIETY. HE right ascension of the Sun at Greenwich and his declination 4° 46′ 27.5" north. He may therefore be said, roughly, to form an isosceles triangle with and Piscium, being at the apex of it. He rises in London on the 1st at 5h. 36m. a.m., and sets at 6h. 31m. p.m.-his rising and setting on the 30th taking place, in the same locality, at 4h. 35m. a.m., and 7h. 19m. p.m., respectively. The equation of time is additive, but diminishing, up to the 14th instant, after which date it becomes subtractive. On the 1st 3m. 47.2s. must be added to the time indicated by a sundial to obtain true clock time, and this quantity decreases to 9-268. on the 14th. Subsequently, on the 15th, 5-59s. must be subtracted from the time shown by a meridian instrument; and, by the 30th, 2m. 58-49s. must be taken away from apparent time to get mean time. The semi-diameter of the Sun at his Greenwich transit is, on the 1st, 16' 17", and this occupies 1m. 4:58. of sidereal time (convertible into mean time by the subtraction of 0.188.) in its passage over the meridian. The semi-diameter will have diminished to 15' 54.1" on the 30th, and this will occupy 1m. 6·018. of sidereal time (convertible as before) in its transit. The sidereal time at mean noon on April 1st is Oh. 40m. 36-248., while on the 30th it is 2h. 34m. 56-31s. The mean time at sidereal noon, or mean time of transit of the first point of Aries, is 23h. 15m. 34.5s. on the 1st, and 21h. 21m. 33 16s. on the 30th. Solar activity is now perceptibly diminishing, and spots are becoming both smaller and less frequent than they have been. The Moon will be New at 31-7m. after midnight on the 7th, will enter her first quarter at 10h. 11-3m. on the night of the 15th, be Full at 1h. 37 2m. in the afternoon of the 23rd, and enter her last quarter at 8h. 20.9m. a.m. on the 30th. She is exactly 23 days old at noon on the 1st, and, of course, 29 days old at the same hour on the 7th. At noon on the 8th her age is 0-5 days, and so on to the 30th, when it is evidently 22-5 days. At 7h. in the evening on April 8th libration will render an additional part of her south-west limb visible, while at 8h. a.m. on the 21st more of her south-east quadrant will come into view from the same cause. The Moon will be in conjunction with Saturn at 4h. 50m. in the afternoon of the 1st, with Venus at 7h. 23m. in the evening of the 5th, with Mars at 4h. 21m. p.m. on the 8th, with Mercury at 8h. 1m. the next morning, with Jupiter 36m. before noon on the 15th, with Uranus at 11 o'clock the same night, and lastly with Saturn again at 11h. 18m. on the night of the 28th. There will be only three occultations of fixed stars by the Moon, and one close approach to a star by her during this month. First, on April 13, 5 Geminorum will disappear at the Moon's dark limb at 6h. 55m., to reappear at her bright limb at 8h. 6m. Then, at 11h. 48m. on the night of the 14th, she will pass quite close to 48 Geminorum. On the 18th, at 7h. 59m. p.m., B.A.C. 3579 will disappear at the dark limb, reappearing at the bright limb at 9h. 16m.; while, later on the same night, i Leonis will be occulted by the dark limb at 10h. 14m., and emerge from behind the bright one at 11h. 10m. Mercury is now an evening star, and attaining, as he does, his greatest eastern elongation (19° 7') at 3h. 11m. a.m. on the 5th, and, moreover, having now considerable north declination, is very favourably situated for observation during the early part of April. His apparent diameter increases from some 7" at the beginning of the month to something like 12" at the end of it. As he does not set until nearly two hours after the Sun during the first part of April, he may be looked for in the evening sky after sunset, a little to the north of west. He travels from Pisces into Aries, but does not pass near any sufficiently conspicuous star for it to be taken as a poor telescopic object. Her conjunction with the Moon at 7h. 23m. on the evening of the 5th has been previously adverted to. Mars, with his minute disc of only some 5" in diameter, is too close to the Sun to be visible. His conjunctions with the Moon at 4h. 21m. in the afternoon of the 8th, and with Mercury at 1h. 20m. a.m. on the 20th, have been before referred to. Jupiter, although rapidly approaching the west, still continues to be the chief and most conspicuous object in the sky, up to, and for a little while after, midnight. He is travelling slowly eastward, through the barren region to the south of Castor and Pollux. He rises on the 1st at 10h. 39m. a.m., souths at 6h. 46.5m. p.m., and sets at 2h. 55m. the next morning-his rising, southing, and setting, on the 30th, taking place at 8h. 58m. a.m., 5h. 3.9m. p.m., and 1h. 10m. a.m. the next day, respectively. 43m. before noon, on the 10th, Jupiter will be in quadrature with the Sun. The effect of this on the interval elapsing between the entry on, or departure from, the disc of Jupiter, of his satellites, and of the shadows which they respectively cast, will be noticed in the list of the phenomena of the Jovian system for this month which we give below. His apparent diameter continues steadily to decrease, from about 40" at the beginning of April, to 36" at the end of it. We have previously spoken of his conjunction with the Moon at 11h. 24m. a.m. on the 15th. Owing to his position with reference to the Earth, the phenomena exhibited by Jupiter's satellites now are decreasing both in number and frequency. During the month of April the following will be exhibited :-Firstly, on the night of the 1st, at 7h. 40m., the transit of satellite 1 will begin. It will be followed by its shadow at 8h. 57m. The egress of the satellite will occur at 10 o'clock, that of the shadow at 11h. 17m. On the 2nd, satellite 1 will reappear from eclipse at 8h. 24m. 6s. A reappearance from eclipse of satellite 3 will also take place at 8h. 3m. 55s. on the evening of the 4th; and it is possible that afterwards, at 1h. 42m. after midnight, the occultation of the 2nd satellite may be perceptible. On the evening of the 6th, satellite 2 will begin its transit at 7h. 59m., its shadow not entering on to the planet's limb until 10h. 32m. At 10h. 54m. the satellite will leave Jupiter's opposite limb, as will the shadow at 1h. 28m. the next morning. 16m. after midnight, on the 7th, satellite 1 will be occulted; while the transit of satellite 3 will commence somewhat later, at 1h. 21m. On the evening of the 8th, at 7h. 43m., satellite 4 will enter on to the face of the planet, satellite 2 will reappear from eclipse at 8h. 25m. 49s., the transit of satellite 1 begin at 9h. 35m., that of its shadow at 10h. 52m., the egress of the satellite at 11h. 54m., that of satellite 4 two minutes later, while the shadow of satellite 1 will not quit Jupiter's limb until 1h. 12m. the next morning. On the night of the 9th, satellite 1 will reappear from eclipse at 10h. 19m. 35s. The egress of the shadow of this same satellite will take place at 7h. 41m. the next evening, the 10th. Perhaps satellite 3 may be perceived to reappear from occultation at 6h. 52m. p.m. on the 11th. It will afterwards disappear in eclipse at 8h. 38m. 198., reappearing from it at 4m. 54s. after midnight. The transit of satellite 2 will begin at 10h. 37m. on the night of the 13th. Perhaps, under very favourable circumstances, the ingress of its shadow at 1h. 10m., and the egress of the satellite itself at 1h. 32m. the next morning, may be discerned. On the night of the 15th, satellite 2 will reappear from eclipse at 11h. 1m. 6s.; the transit of satellite 1 will commence at 11h. 30m., its shadow come on 47m. after midnight, while it is conceivable that the egress of the satellite may be caught at 1h. 49m. At 8h. 40m. on the night of the 16th satellite 1 will be occulted, to reappear from eclipse at12h. 15m. 58. The shadow of this same satellite may perchance be detected in its entry on to the planet, at 7h. 16m. in the evening of the 17th; the egress of the satellite casting it occurring at 8h. 18m.; and the shadow itself passing off at 9h. 35m. Later, satellite 4 will reappear from eclipse at 10h. 22m. 338. On the 18th it may happen that the occultation of satellite 3, at 7h. 25m., may be discernible. It will reappear from occultation at 10h. 55m., only, however, to suffer eclipse at 12h. 38m. 11s. It may happen that the ingress of satellite 2 may be detected at 1h. 16m. a.m. on the 21st. Satellite 2 will be occulted at 8h. 13m. on the 22nd. The transit of satellite 1 will begin at 1h. 26m., and satellite 2 morning, but the observation of these phenomena is problematical. On the night of the 23rd, satellite 1 will be occulted at 10h. 37m. The beginning of the transit of satellite 1, at 7h. 55m., and the egress of the shadow of satellite 2, at 8h. 2m., on the evening of the 24th, may possibly be caught. Afterwards, the ingress of the shadow of satellite 1 will commence at 9h. 10m., the satellite leave the planet's face at 10h. 14m., and the shadow at 11h. 30m. Satellite 1 will reappear from eclipse at 8h. 39m. 31s. on the night of the 25th, and satellite 3 be afterwards occulted at 11h. 30m. The egress of the shadow of satellite 3 will happen at 10h. 7m. on the night of the 29th; satellite 2 will subsequently be occulted at 10h. 52m. Lastly, it is just possible that the occultation of satellite 1 may be perceptible 34m. after midnight on the 30th. Saturn, in his old quarters in Sagittarius, continues in a deplorable position for the telescopic observer. He rises on the 1st at about a quarter to 3 a.m., souths at 6h. 49·1m. a.m., and sets at 10h. 53m. a.m. On the 30th his rising, southing, and setting take place at 54m. after midnight, at 4h. 58m. a.m., and at 9h. 2m. a.m., respectively. He will be in quadrature with the Sun 35m, after noon on the 10th. Reference has previously been made to his conjunctions with the Moon, at 4h. 50m. p.m., and 11h. 18m. p.m., on the 1st and 28th, respectively. Uranus, like Jupiter, is travelling towards the west, but is still observable during a good deal of the working part of the night. The directions given for finding him last month (Vol. XIV., p. 576) are equally available for the present one, as his movement is so extremely slow. His diameter remains stationary at 4". He is in quadrature with the Sun at 10h. 41m. on the night of the 16th. We have spoken, under the proper heading, of his conjunction with the Moon at 11h. p.m. on the 15th. When we have said that Neptune is in conjunction with the Sun at 9h. 5m. a.m. on the 13th, it will scarcely be necessary to add that he is wholly invisible during April. Shooting stars would appear to be tolerably common in the month of April. Suspicion exists of a periodical shower at some period between the 4th and the 11th, while a pretty well ascertained one is referred to in the B.A. report for 1870 as occurring between the 19th and 21st of the month. WEATHER CHARTS. THE first four weather charts of the Meteor ot logical Office, March 16 to 19, 1872, at 8 a.m., are now before us. The arrangement is good, the land being shaded and the water white. On the left hand we have the weather reports, and on the right the chart for the day, which consists of four maps; one for depicting the isobars, one the isotherms, a third for the general direction of the wind and state of the sea, and a fourth for giving a statement of cloud, rain, &c. So far the general description. A word on the utility of the charts may not be out of place. Confining our attention to the barometer and temperature, a glance at the four charts will convince us that the area embraced by the maps is but small, the isobars and isotherms being inere fragments. The directions and values of these lines are the only elements of pressure and temperature attainable from the charts. The relation of the meteorology of the British Islands and France to the Continental area on the east and the oceanic area on the west is unattainable, and these relations are of the first importance in judging of the progression of weather. 16th we had the barometer ranging from 30 to 29-57, being a gradient N.N.W. of about >> On the On the 17th the directions of the lines were altered, running S.W.-N.E. instead of W.S.W. -E.N.E. We are, however, entirely ignorant of the barometric state of the countries in advance of these lines, and quite as ignorant of the nature of the isobars likely to succeed them. This is particularly illustrated in the isobaric chart of March 18, a new system being manifested over the whole of the area. This great and decided alteration in the direction and value of the isobars shows that a single telegram daily is insufficient, according to our views, for the requirements of meteorology. The most valuable feature of the charts is the connection between barometric pressure and wind. In this notice we cannot enter into a description of the relation existing between the two, further than saying that the wind maps show unmistakably that the general course of the wind is parallel to the direction of the isobars. COMPRESSED AIR AS A MOTIVE POWER. with which the cars are drawn by horse-power. It is in the direction of applying compressed air as a motive-power for tramway cars, however, that experiments have been carried out which bid fair to lead ultimately to success. In several instances cars have been propelled by compressed air, but as the apparatus employed is only regarded as tentative, the details of the mechanism and the characteristic action of the air have not been published with sufficient minuteness to enable an accurate estimate to be made of the power obtained and of its cost. The necessity of some improved means of transit in cities is acknowledged on all hands, and as we know that "Necessity is the mother of Invention," it will probably not be long before some economical, easily-controlled force is applied to the propulsion of street cars, at all events in America. We have already illustrated the American ammonia engine, and we recently described a steam car in course of construction in this country; but we think that compressed air will ultimately be the chosen means of propulsion. Mr. J. A. Whitney, in a paper read before the New York Society of Practical Engineering, after alluding to the objecWE E have had occasion within the last twelve tions against the employment of steam in carriages months or so to call the attention of our traversing public thoroughfares, and protesting readers to the progress which is being made in against its use for underground railways in tunnels the application of compressed air as a means of without openings, declared that horse power is obtaining motive power. In this country ma- acknowledged to be inadequate to the wants of chines have been constructed, and we believe New York street railways; the transmission of with satisfactory results, which are put into mo- power by ropes, as illustrated in the elevated tion by the expansive force of air compressed by railway on Greenwich-street, has proved a means of water or suitable steam-engines, the "mediocre and insufficient method of propulsion," power being conveyed to the scene of its opera- and it is only in pneumatic power that he contions in pipes, the length of which is practically siders sufficient promise of success appears to unlimited. So far as we know, however, com- justify the outlay required to thoroughly test the pressed air has not been employed in this principle. The plan, which has hitherto given the country for obtaining motion, except in those best results, consists in compressing the air to a cases where it is almost impossible to use steam- very high degree, and storing it in tanks or for instance, in coal-mines; and an account of cylindrical chambers arranged about the body of its successful application to colliery working will the car in the most convenient manner; from be found at p. 2, Vol. XIII. In the United these the air is led to a receiver supplying the States, on the contrary, compressed air as a cylinders, which are constructed in much the motive power has received more than usual at- same manner as those of steam-engines. In all tention, especially since its value was proved this there is, of course, but little difficulty; if air beyond doubt by the operations at the Mont is compressed to, say, 200lb. on the square inch, Cenis tunnel, and American engineers and inven- and is then allowed to exercise its elastic force on tors have been both experimenting and theorising a piston fitting closely in a cylinder, we can on its capabilities and the best methods for its calculate approximately the amount of power utilisation-its application to locomotion being the piston should exert, but if we omit to the principal object sought by our cousins. take into consideration the surrounding conIt is actually more than 60 years ago since Med-ditions and the peculiar characteristics of hurst proposed to drive carriages through a brick expanding air we shall, without doubt, make tunuel by means of an air-blast, and various projects for accomplishing a similar object have been introduced, but have invariably failed, either from mechanical difficulties or from the absence of any economy-perhaps we should say from the great expense incurred in keeping the apparatus in working order. Probably the most notable of all these attempts was the Atmospheric System tried on the South Devon Railway, in 1847, by Brunel, which although successful as far as the mere propulsion of the trains was concerned, was yet so hampered by constantly recurring difficulties that it was finally abandoned by the directors, for "prudential reasons. The principle of this atmospheric system, which was patented by Clegg and Samuda, consisted in a tube containing a close-fitting piston, which was driven along by the pressure of the air behind it, a vaccuum being created in front of it by means of powerful steam-engines. The tube had a slit in its upper surface which was covered by a valve of leather, and through this slit the bar connecting the piston with the carriages passed. It is obvious that the construction of a valve which should fit with the requisite closeness, and yet open readily, to allow the passage of the connecting bar, must necessarily be a work of great difficulty, requiring much ingenuity and skill for its accomplishment; and it is no wonder, therefore, that in the early life of the system, before experience had been gained by extended trials, many failures should have occurred, and that even Brunel should have recommended no further persistence in the attempt. It was, however, the opinion of many persons at the time that, given the requisite funds, the atmospheric system might eventually have triumphed, and the defects in the original apparatus have been successfully remedied. a grievous mistake in our calculation. Most of our readers are aware that when compressed air is allowed to expand it robs the surrounding matter of all the heat it can, and, indeed, by virtue of that property has been used for refrigerating purposes. It will be evident, therefore, that unless the air is considerably raised in temperature, or the cylinder heated by means of water or hot air circulating in a jacket, that whatever moisture may be contained in the compressed air will be converted into ice, which will speedily block up the exhaust port and the pipes connected with it, as well as lower the temperature of the air in the reservoir. To obviate this difficulty one inventor proposes to construct the main reservoir of a material which will prevent the loss of heat, and consequently of power, by radiation-the air in the process of compression becoming, of course, considerably raised in temperature-heat which it is desirable to retain; another proposes to pass the pipe conveying the air to the cylinders through the warming apparatus of the car; while a third suggests an arrangement whereby the air from the stove used for warming the car should be made to circulate in annular jackets round the cylinders. Independently of the fact that the stove is not always in requisition to "warm the car," e.q., in the summer, these plans are open to objection on several grounds; and it appears to us that the proposal to heat the cylinders by means of jackets containing hot water is to be preferred, as the water could be changed at the end of each journey, and facilities would be also afforded for warming the air of the main reservoir, in which the refrigerating effect would be experienced during the early part of the piston stroke. Another proposal has for its principal feature the heating of the air by burning hydrogen or carburetted hydrogen in a vesA resuscitation of the old system has been sel near the cylinders. The hydrogen is compressed frequently proposed of late in the United States to the same degree as the air, and burns in jets for the motive-power of trains in tunnels to be in the air which passes through the above-menconstructed underneath the crowded and busy tioned vessel on its way to the cylinders. The streets of the principal cities; for although gas is to be set alight by means of electricity: so rs are there as common as lampposts, that the apparatus for working the car would and incapable of accommodating the become a trifle too complicated and expensive, we consequence chiefly of the slowness think. It will be apparent, then, to our readers that there is nothing impossible in the proposal to run street cars by means of compressed air-in fact, it has been done, and an account of a trial of one at Chicago will be found on p. 345, Vol. XII., in which it is stated that the only fault was the noise made by the exhaust of the engines. This latter can be easily remedied, and the escaping air used to cool the atmosphere of the car in summer and urge the fire in winter. The next question, then, is in reality the main point. What is the cost? There is, first of all, the construction of the reservoirs, which for the sake of lightness must be of steel or copper; and then there is the requisite apparatus for compressing the air, which must be supplied in duplicate, one for each end of the road, for the weight of the car would scarcely be increased for the sake of storing sufficient air for a double journey. The other expenses would be much the same as now, so that it is a matter of comparatively easy calculation to approximately ascer tain the first outlay, and whether the increased comfort and speed of travelling could not be obtained for the same amount as is now paid for horseflesh. The system would doubtless be more expensive than steam; but there are "obstructions" to the introduction of the latter which could not well be thrown in the way of compressed air. Mr. Whitney, who is perhaps rather enthusiastic in the matter, believes that passengers may be cheaply carried at a speed of from 20 to 40 miles an hour "with all the comfort of ordinary railways, and none of the dangers or inconveniences incident to the employment of locomotives." His proposal for a pneumatic railway will show how far in this direction the ideas of the Americans are advanced. "An elevated pneumatic tube is to be carried over the buildings and cross-streets, sustained on iron supports constructed on the principle of a suspension bridge over each block; this tube is to be of wrought iron for strength and lightness; lined with wood for moderate warmth and for reduction of friction to the air blast; glazed throughout its length with panes sufficient in size and number to light it well; furnished with switches, to enable a car to be stopped at a station without interference with the others; farnished with electric signals automatically actuated by the cars themselves, to indicate their approach to the stations; the working of the line to be placed, from the lowest duty to the highest, in the hands of educated, careful and properly remunerated engineers, and the question of quick transit, in one of its phases at least, will be solved with greater satisfaction to the public and credit to the engineering profession than the most ardent advocates of speedy passenger travel now dare hope for." Whether the system will be adopted in this country for propelling street-cars will probably depend in a great measure on the success of the attempt in America; but as a means of obtaining coal that is otherwise out of reach there can be no doubt of the great utility of the compressed-air apparatus. Machines for getting coal are capable of working in a temperature where muscular exertion is almost impossible; and the air having done its work in actuating the apparatus will cool the underground passages, and enable human beings to penetrate much deeper into the crust of the earth than they have hitherto succeeded in doing. THE METALLURGY OF IRON AND STEEL. of lectures on the above subject delivered by Dr. Percy, F.R.S., in the lecture theatre of the Geological Museum: We have heard of precious metals, noble metals, and base metals: but if a metal is to be judged noble in respect of its utility to mankind, iron holds the highest rank. It is extremely widely diffused, is," in fact, everywhere; however deep we go iron is to be found, and it is a large constituent of many rocks. It exists even in our blood, and without it we could not live. I have seen sufficient iron taken from out of a man's blood to make a medal. Iron ores contain always the metal in a state of combination, the only case in which we are acquainted with the native metallic iron is that of meteoric iron. This comes probably from some interplanetary spaces-we know not where and occasionally masses of it have dropped down on our earth, varying in weight from ounces to tons. Red oxide of iron, or red iron ore, is one of the most important ores in this country; it is now largely in demand for making the metal suitable for the Bessemer steel process, and on this account has lately risen to double its former value. It occurs in large nodular, sometimes "kidneyshaped" masses, and occasionally crystallised, and presenting a bright metallic lustre, when it is known as specular iron ore." In all these cases it contains the same proportion of chemical elements, and these are iron and oxygen. Oxygen forms about one-fifth of the atmosphere; without it no combustion could occur, no human being could live. The metals have a strong affinity (or liking) for oxygen. A steel spring burns in it with vivid scintillations. Placed in a jet of flame, from a mixture of coal gas and oxygen, the combustion is very striking. If we take a piece of metallic iron and leave it exposed to the air it soon becomes covered with rust. This rust is the oxide of iron, being nothing more than a combination of the metal with the oxygen of the air; in most cases a certain proportion of water is added. If we take a piece of iron, heat it, and keep it for a long time, it undergoes a change. It increases considerably in weight; and if the heat be continued, especially if the metal be finely divided, as in the state of filings, it becomes converted into an oxide just like the above ore. There is still another way of producing this oxide, -namely, by dissolving the metal in an acid (as muriatic), and then precipitating it by the addition of another substance (as potash or ammonia). If this oxide of iron be rubbed on a piece of paper it will always give a distinct red mark, and never a brown or black one, and in this way we can distinguish between one kind of iron ore and another. This ore, when perfectly pure, contains 70 per cent. of metallic iron. Some of it is used for a very important purpose-viz., burnishing, and when you get hold of a good bit it is worth a good deal of money. It is also used as a pigment, the so-called Indian red and Venetian red are oxides of iron. lishing plate glass, for which purpose the oxide Also for pois ground and washed in water, and after the coarser particles have settled the liquid is poured off, and the finer particles for use allowed to subside, and thus they are obtained in a state of great tenuity, Rouge, used for polishing silver, is also an oxide of iron, and the oxide is also frequently used for adulterating "red lead." It is found in Cumberland and Lancashire, and is very much in request on account of its purity; large quantities are now imported from Spain. Another kind of iron ore is called brown iron ore; it is nothing more than the red ore combined with water, and may be called a natural rust. There is a great deal of it in various parts of the world; much in the Forest of Dean, where it has been worked since the time of the Romans. When perfectly pure it contains 59.89 per cent. is also more or less coaly matter, and when that hide, and he can work one with each foot. reaches eight or ten per cent. it gives a dark Another example of Indian bellows was shown, colour to the ore, which is thence called "black consisting of the skin of an animal sewn up, exband." They are called "clay " iron ores because cepting a tubular portion (for the nozzle) at one the nodules resemble clay; they are found in end and a longitudinal slit at the other. The many parts of the world. They are not confined edges of this slit were fastened to two sticks; and to the coal-measures, but are also found in the the bellows were worked by setting one end of the Weald of Sussex-the iron railings round St. sticks firmly together on the ground as a fulcrum Paul's are made from Weald iron ores. The for the leverage, and working the other backCleveland iron stone is mainly a carbonate of wards and forwards, closing the sticks as you iron. advance it to force out the air, and opening them on withdrawal. If the hide be supple a good blast can be thus obtained. Iron varies notably with the kind of ore from which it is made, but this depends not on any difference in the metal itself, but in the presence of certain impurities varying in nature and proportion. In the extraction of iron the ore is in every case treated as an oxide. If we take the red oxide there is nothing more to do in that respect; the brown variety must be heated to drive off the water; the magnetic ore requires no further treatment; the clay and sparry ores must be previously raised to a red heat to drive off the carbonic acid. Thus in every case we find, without exception, that the material treated for the purpose of obtaining iron and steel is the oxide of iron. If we take the oxide and reduce it to powder, and mix with it a small quantity of charcoal, and then heat it in a closed vessel for a short time, the charcoal will remove the whole of the oxygen. This process requires a very high temperature. If we take a lump of oxide and simply imbed it, in red hot charcoal, and keep it so for a few hours, we shall find that every particle of the oxygen will be perfectly removed from it, and there will remain a mass of workable, metallic iron. It is not even essential that there should be extensive contact between the ore and the charcoal, it is sufficient to imbed the former in the latter. A third kind of bellows-double acting-was exhibited, as used in China and Japan, the one in question having been used by an itinerant tinker in China. It consists of a rectangular box, closed at bottom, but with a movable lid, and a hanging valve at each end, cpening inwards. Inside is a piston worked by a bandle outside, and having a packing of cocks' feathers. On the bottom is a canal running the whole length, with an opening on the top into the box at each end. The exterior opening (in reality two) is about halfway of the length of this canal, inside of which valves are placed to regulate the passage of the air during the working of the piston. This apparatus works remarkably well, giving a good, practically continuous blast. c. (To be continued.) LESSONS ON CHEMISTRY.* (Late of the Istituto Bellino, Novara, Italy.) (Continued from p. 4.) CHLORINE TETROXIDE.-Synonym: Chloric Oxide.1 Symbol: CIO", or Cl2'O"? Molecular weight: 67.5. colour, with a smell resembling that of We have heard of the stone age, the bronze age, and the iron age, and are told that they occur, in and tin, usually 10 per cent. of tin, and the pro- chlorine, though not so pungent and suffocating. Its this sequence. Now bronze is an alloy of copper 110-PROPERTIES.—A gas of a deep yellow duction of bronze would imply a considerable specific gravity is 2-3365, or, what amounts to the degree of advance in the art of metallurgy, as both copper and tin had to be extracted from their same, it is about thirty-four times as heavy as ores. They require to be melted together in bydrogen, hence we are led to conclude that its proper proportions, and then to be melted again molecule contains only one atom of chlorine, and cast. Metallurgically speaking, one would united to two of oxygen, and not two of chlorine expect to find, other circumstances being clear, to four of oxygen (see foot-note referring to that the iron age would be next after the stone chlorine trioxide). In common with the comage. Iron is so very readily destroyed by corroding, pounds just examined, it possesses great bleachwhile bronze endures well, that it is no wonder if ing powers. It may be condensed to a red liquid iron was used by these early people, that it has at a temperature of about-4° Fahr. It is a most not come down to us. In the Assyrian collection dangerous body to operate upon, as it is liable to in the British Museum are some very interesting explode with a very slight rise of temperature, objects of iron and steel, which show that these sometimes fracturing the containing vessel, and people were well acquainted with the use of iron, solves freely in water, but does not appear to thereby endangering the experimenter. It disand that it was plentiful and cheap we may infer unite with it to form an acid, though the solufrom the fact that they used it for hammer tion formerly went by the name of hypochloric acid. This solution, when placed in contact with chlorite and a chlorate of the metal employed. metallic oxides, gives rise to a mixture of a Up to the present time chloric oxide has received no practical application. metallic iron and 14.5 water. Ochres are an heads. The third kind of ore is magnetite or magnetic In other instances, in ancient times and at the present day, in countries where it is commonly said that civilisation is not advanced, the process for extracting iron from its ores is essentially a reduction of the oxide by means of charcoal. They take a small furnace, often not larger than an ordinary chimney-pot (cost about three halfpence); this is lined at the bottom with fire-clay, or the best substitute they can get, and has a hole by which to admit the air. These are sometimes circular in section, sometimes rectangular, and frequently the bottom is made to take out. They next reduce the ore to coarse gravel, and place it in the furnace in layers, alternating with layers of charcoal. To keep up a continuous blast, if they have not a double acting bellows, two or three pairs of bellows are worked in alternation. The oxygen is removed, and with the charcoal forms carbonic oxide, which burns at the top of the furnace. After working hard at the bellows for some hours, the ore is reduced, and the iron forms a metallic mass at the bottom of the furnace. The lecturer then described a kind of bellows used by the Hindoos, who have, no doubt, bellows properly so called, but use a kind of which one man can work two alternately, and so keep up the blast. It consists of a rude piece of wood with a cavity hollowed out, and covered over by a piece of supple buffalo hide. In the hide over the centre of the cavity is a hole through which a string passes, and is fastened to a small peg to prevent it drawing through. The other end of the string is fastened to a long bamboo spring, which thus keeps the hide stretched. A bamboo tube leads the air from the side of the bellows to the furnace. They are worked by a man covering the hole with his heel, at the same time pressing down the 111.-PREPARATION. A small quantity of potassium chlorate is made into a paste with sulphuric acid. The mixture assumes & deep yellow tint, and is then to be introduced into a retort, which must be carefully heated with warm water (bain marie). Chlorine tetroxide is evolved, and may be collected by downward displacement, as water decomposes it, and mercury is attacked by it. The interchanges which take place during the action of sulphuric acid on potassium chlorate occur in two phases-viz., 1st. The production of chloric acid and sulphate of potassium; 2nd. The splitting of chloric acid into water, perchloric acid, and chloric oxide. The following equations may serve to illustrate these changes :1st Phase. 2nd Phase. 3H'C1'0" H2'0" + H'CI'О" + 201′0′′. 112. The formula of chlorine tetroxide may be represented in two modes, according to the view taken of its constitution. If we take the view, with some, that an open chain (see 26) cannot exist in the free state for an appreciable The right of translation and reproduction is reserved. 1 Peroxide of chlorine. 2 Acording to some, water decomposes the gas, splitting it up into chlorous and chloric acids. 8 See paragraph 114 in explanation of the term "chlorate." D. CHLORINE PENTOXIDE.-Synonym: Chloric anhydride. Symbol: Cl'Os" (?). Molecular weight: 151 (?)." 113. This body is as yet unknown in the separate state. In combination with the elements of water it exists in chloric acid, to which it bears the same relation as the hypochlorous and chlorous anhydrides bear to hypochlorous and chlorous acids. D (2). CHLORIC ACID. Chlorate. weight: 84.5. 114.-PROPERTIES.-An oily, colourless fluid, of a strongly sour taste. It reddens vegetable blues, but does not possess bleaching powers. It has never been obtained entirely free from water, for on reaching a certain point of concentration it is decomposed with evolution of oxygen. Heat also effects this decomposition, resolving chloric acid into a higher oxide of chlorine, viz., perchloric acid and oxygen. In fact, its most marked property is the facility with which it parts with its oxygen. For this reason it is a most powerful oxidising agent. A few drops allowed to fall on a piece of paper cause it to ignite, owing to the rapidity with which oxidation takes place (see paragraph 80). In contact with metallic oxides, chloric acid gives rise to a metallic chlorate and water; thus:· Synonym: Hydrogen Symbol: H'CI'O". Combining " M2'0" + 2 H'Cl′03′′ = 2M′ Cl′03′′ + H2O. The chlorates are all soluble in water; and on heated split up, as we have already seen (87), into oxygen and a chloride, thus : M"CIO," = M'CI' 30". Hence potassium chlorate is a most convenient source of oxygen. 115.-PREPARATION.-On passing a current of chlorine through a solution of potash or soda, or through a stratum of slaked lime, if the temperature be kept low, a mixture of a chloride and a hypochlorite is produced (see 103), but if the temperature is high, or the resulting compounds be afterwards heated, no hypochlorite is formed (as the hypochlorites are all decomposed by heat) but a chlorate of sodium, potassium, or calcium, as the case may be, mixed with a corresponding chloride. The resulting chlorides, being much more soluble in water than the chlorates, remain in the mother liquor on allowing the solution to crystallise. From the potassium chlorate K'Cl'O", chloric acid may be easily obtained, by dissolving it in water and allowing a body called hydrofluosilicic acid H, SiF to act upon it; when a substition of the potassium in the chlorate for the hydrogen in the acid takes place, and chloric acid, together with potassium silico-fluoride, are the results, thus: 2K/C1'0"+H2'Si""F'=K, 'Si"'F' +-2H' C1'03". The silico-fluoride is insoluble in the resulting chloric acid, hence it may be separated from it by filtration through asbestos, or by decantation. By treating barium chlorate with sulphuric acid this latter seizes on the barium and liberates the chloric acid. The chlorate must be dissolved in water, and the sulphuric acid (previously diluted and cooled) added gradually as long as a precipitate of barium sulphate is formed: this Chloric acid. Barff., 1871. Hydric chlorate. 1871. 6 Mother liquor, a term used to denote a solution which has furnished crystals. Ba"2C1'0"+H,'S"," Ba"S"O"+2H' CI'O". In both these processes, the resulting chloric acid contains a quantity of water, which may be partially removed by careful evaporation under the receiver of an air pump, under which stilThe molecular constitution of chloric acid may be phuric acid is also placed to absorb moisture. represented graphically thus:— H " However, as chloric acid has never been obtained in the state of vapour, this must not be taken as certain all we know is, that for every atom of chlorine in this compound there are three atoms of oxygen and one of hydrogen. Hydrogen chlorate, or chloric acid, was first isolated by Gay-Lussac. E. CHLORINE HEPTOXIDE-Synonym: Perchloric Anhydride. Symbol: Cl'Or" (?). Molecular weight: 183 (?) E (2). PERCHLORIC ACID. Synonym: Hydrogen Perchlorate.8 Symbol: H'ClO4". Combining weight: 100.5. 117.-PROPERTIES.-Perchloric acid, the most stable of the oxy-acids of chlorine, is, when pure a syrupy, transparent, and colourless fluid, which has been cooled to 31° Fahr., without solidifying. It is very volatile, and fumes when exposed to the air, owing to its powerful affinity for water. Its specific gravity at the ordinary temperature is 1.782. The readiness with which it parts with its oxygen when in presence of oxidisable bodies causes it to be one of the most powerful oxidising agents known. A drop allowed to fall on any combustible, such as wood, paper, charcoal, &c., produces combustion with explosive violence. Like most acids, it reddens litmus paper; but it possesses no bleaching properties. It combines with water to form a white solid crystalline hydrate, which melts at 122° Fahr. The composition of this hydrate is H'Cl'O," + H2'O". This hydrate is almost as powerful an oxidising agent as perchloric acid itself. If these crystals be dissolved in water, they form a solution which resembles very much the pure acid, being like it of an oily aspect; it boils at the constant tempe rature of 392° Fahr. This solution contains 72.3 per cent. of real acid, which corresponds to the formula, 9H'C'O," + 19H,'0".10 İn combination with metals, perchloric acid forms a series of compounds called perchlorates, the general formula of which is M'ClŌ". As in all other cases where temperature, it gives off oxygen. After some time the fluid mass begins to thicken, and at last assumes a dough-like consistence. If the heat be withdrawn at this point, the mass is found to be a mixture of chloride, chlorate, and perchlorate of potassiam. On treating this mixture with hydrochloric acid, the chlorate is decomposed, while the perchlorate remains unchanged; washing with a small quantity of water removes the chloalmost insoluble perchlorate remains behind. ride, which is very soluble in water, while the From potassium percholate perchloric acid may be obtained by distilling it with sulphuric acid, which seizes on the potassium, setting free the perchloric anhydride, which instantly unites with the liberated hydrogen of the sulphuric acid to form perchloric acid, thus:2K'CI'O" + H,'S"O" FIG. 10 = K,'S"O" + 2H'Сl'O”. 3rd. Potassium perchlorate may also be prepared by adding well-dried and finely-powdered potassium chlorate, in small portions at a time, to an equal weight of sulphuric acid, and gently warming in an evaporating dish (Fig. 10). The sulphuric acid first liberates the chloric acid from the chlorate; but this is immediately decomposed by heat, and converted into hydrogen, chloride tetroxide, and perchloric acid, which combines with part of the potassium, thus :— 6K'Cl'O" + H2'S","′′ = 3K,'S”0′′ + CH'CI'О", and then 2 replaced by the metal, thus— = Cl2'0" + H2'0" H'CI'O+H'Cro', or, in words, one molecule of water, and one of perchloric anhydride, give rise to two molecules of perchloric acid, or hydrogen perchlorate. 118.-PREPARATION.-Three processes will be described:-1st. By boiling a solution of chloric acid it is converted into water, chloric oxide gas (which escapes), and perchloric acid, thus :H2'0" + Cl2'O," + H'сl'О,". 2nd. On heating potassium chlorate it melts, and if kept in gentle ebullition, without raising the and 2 to perfect unison, by a method to be lantern; a little ball of good cork, 6mm. in diadescribed. No. 1 was placed before a magic meter, was suspended by a silk thread against one of its prongs; the images of fork and ball were projected on a screen. No. 3 had a little wax attached to one of its prongs, so that it gave two beats in a second with No. 1 or No. No. 4 had its extremities filed, and also gave two beats per second with No. 1 or No. 2. Thus No. 4 gave 2 vibrations per second more than No. 1, while No. 3 gave 2 vibrations less. The following were the experiments:— 2. EXPERIMENT 1.-Fork No. 2, attached to its case, and held in the hand, is put in vibration at a distance of 30ft. to 60ft. from No. 1 (projected on the screen as above mentioned.) The ball is driven from the prong of No. 1, which vibrates in unison with No. 2. 30ft. from No. 1, holding fork No. 2 in one hand EXPERIMENT 2.-I placed myself at a distance of and its case in the other. I then set the fork vibrating and moved rapidly towards No. 1. When my movement had become uniform I placed the fork on its case, and did not remove it till just before stopping. Although I came to about a foot distance from No. 1, the ball continued in contact with the prong. EXPERIMENT 3.-I again approach fork No. 1, as in Experiment 2, but without removing the fork from its case after having attached it. The ball did not move till I stopped. At that moment my assistant, who held his ear near the case, while he watched the screen, noticed No. 1 fork vibrate and the cork leap from it. EXPERIMENTS 4 and 5.-I moved away from No. 1 instead of towards it. Results the same as in Experiments 2 and 3. to 256 vibrations per second from a fixed point; A NEW FIRE-ENGINE. being blown through the air vessel on the top are wasted for a minute or two, the apparatus connecting the water and gas cocks is then adjusted, and the machine is ready for use, two minutes being ample for bringing it into full operation. The three-way cock on the delivery nozzle is shut off, and the pressure in the air or gas chamber, shown by the gauge on the top or on the tank, is brought up to 150lb. on the square inch. A pipe of any convenient length, and about lin. and on the end of the pipe a discharging nozzle is attached capable of furnishing a single jet, a spray, or a fine mist. On the inside of the discharging nozzle a pressure gauge is fixed, so that the fireman may keep the point of discharge at 150lb. pressure on the square inch. EXPERIMENT 6.-I set No. 3 vibrating as in HE annexed diagram is an illustration of a in diameter, is then connected with the machine, Experiment 1, this fork making 254 vibrations per second. The ball did not move. Then I removed the fork from its case, and placing myself 30ft. from No. 1, I swung the case in my hand towards No. 1 at a quickness of 8ft. to 9ft. per second, and, while making this forward motion. I put No. 3 above the case. The ball was suddenly thrown from No. 1. When the motion of the case was increased or diminished the vibrations of No. 3 did not affect No. 1. EXPERIMENT 7.-Fork No. 4, which made two vibrations per second more than No. 1, was substituted for that employed in Experiment 6, but placed on the case in its backward movement from No. 1. The results were the same as in Experiment 6. EXPERIMENT 8.-I placed No. 3 before the lantern, and swung No. 1 as in Experiment 7, with the same result. EXPERIMENT 9.-I placed No. 4 before the lantern, and swung No.1 as in Experiment 6, with the same result as in Experiment 6. By these simple experiments I have been able to prove the change in wave-length produced by the translation of the vibrating body. By analogy they perfectly explain the modern method of determining the motions of a celestial body by variations in the refrangibilities of its ray's motions, which it is often impossible to ascertain by any other means. It may be useful to offer some remarks on the details of these experiments, which must be attended to in order to succeed. The forks 1 and 2 must be really in unison. It may happen that two forks vibrating together give no appreciable beats, and are constrained into giving the same number of vibrations per second; while, by making them vibrate separately, the equality is destroyed. I adopt the following method. Having taken three forks, warranted to make the same number of vibrations in a given time, I load one of them so that it gives two or three beats per second with one of the other two which I wish to bring into complete unison. I determine the interval of time between twenty or thirty of these beats by a chronograph. I then determine the interval between the same number of beats with the second fork; and if it is different from that obtained with the first, I attach wax to the more rapidly vibrating fork till it makes the same number of beats as the slower. Having thus adjusted the forks, I have had no difficulty in Experiment 1 at 60ft., and believe the effects would be the same at 100ft. The cork ball should be spherical, and should not do more than touch the fork. It is advisable to varnish the ball. A machine has been invented by which one' can communicate a uniform motion of translation to the forks. A small mirror held between two vertical threads may be substituted for the cork ball, giving very delicate indications by the motion of a reflected ray. The fork No. 1 makes 256 complete vibrations per second; while No. 3 makes 254, thus giving for wave lengths, 4-367ft. and 4.401ft. respectively, reckoning the velocity of sound at 1,118ft. per second. M. Mayer then proves that 256 vibrations of a fixed body will produce the same effect on a distant surface us 254 vibrations of a body which approaches the surface with a speed of 2X, or twice the wave length of the No. 1 fork-i.e., 8-734ft. per second, which was the speed given to the fork in Experiment 6. fire-engine on an entirely new principle patented by Mr. Thomas Atkins, the main features of which will be gathered from the following description. In the trials made recently at Welwyn very satisfactory results were obtained, a fire made of faggots smothered with tar being brought completely under control for an hour, and finally extinguished when its purpose was served, at an expenditure of two and a half gallons of water. The principle of the invention consists in charging the water used with carbonic acid and nitrogen, but its chief novelty lies in the remarkably cheap method of obtaining the carbonic acid, which is made by drawing the atmospheric air through a charcoal fire and forcing it into a tank containing water. This tank is 2ft. 6in. long by 2ft. wide, and 2ft. deep. The vacuum chamber, which connects the pump with the water to be used in the tank is lft. in diameter and 2ft. deep. The pump is 4in. in diameter, double action, 10-in. stroke. On the left hand side is a small stove, with a pierced ring in its interior; this stove is 9in. in diameter and 14in. deep, with a ventilator in the bottom for admitting air to the stove, and a door and frame fitted air-tight to the top, 3in. in the Take next the case of light. Suppose that the clear, to admit fuel. A small pipe runs from the fork No. 1, which makes 256 vibrations per second, stove about 18in. high. Half way up the pipe is made 595 millions of millions of vibrations, the a small pulse-valve for preventing back action number belonging to ray D in the spectrum. from the pumps in case of leakage, and so adThen the fork No. 3 will represent 590 millions justed as to work in harmony with a foot-valve in of millions of vibrations per second, which will give us а wave length 0000042 mm., greater than that of D, and which nearly corresponds to a line of iron situated 43 divisions above D, in Angström's map. We have seen that the fork No. 3, giving 254 vibrations per second, must approach the ear with a speed of 8-734 feet to produce the note belonging the vacuum chamber that supplies the water to According to the inventor, the gases generated and poured into a glass 6in. long, at the pressure before-mentioned, are retained in the water for several minutes, and when thrown upon the fire sink to a temperature of from 40° to 50° Fahr. One cubic foot of this fluid discharged upon any burning pile is capable of doing as much execution in extinguishing fire as 50 cubic feet of water from an ordinary fire-engine, and in onetwentieth part of the time now occupied, while the results are said to be unfailing. Under the arrangements proposed by the inventor, fire-engines will, he thinks, be of little use, as new conditions will be submitted entirely altering our present notions of dealing with fire. A large skeleton map of London is being prepared, indicating 2,500 receivers or store vessels. These may be fixed in cellars, under pavements, or in warehouses. The contents of such vessels will vary from 150 to 1,000 gallons of water charged with carbonic acid. Pipes, valves, and all necessary apparatus will be attached to these stores, which may be instantly brought into operation, and a fire extinguished by merely turning on a tap and allowing the water to fill the building in the form of spray. Another important point is the capability of the invention to instantly depolarise vast quantities of sulphurous vapours, carbonic acid gas, carburetted hydrogen, and sulphuretted carburetted hydrogen. A delivery jet of in. in dia |