22 British Association for the Advancement of Science. { American Chemical Society.-At a meeting of American chemists, held in April last at the New York College of Pharmacy, it was resolved to form a society, to be called "The American Chemical Society," and at a subséquent meeting the following officers and committees were appointed :-President-John W. Draper. Presidents J. Lawrence Smith, Frederick A. Genth, E. Hilgard, J. W. Mallet, Charles F. Chandler, Henry Morton. Corresponding Secretary-George F. Barker. Treasurer-W. M. Recording Secretary-Isidor Walz. CHEMICAL NEWS, TO CORRESPONDENTS. H.Cant.-Hopkin and Williams, or from Dr. Theodor Schuchardt Chemische Fabrik, Gorlitz. THE Vice- QUARTERLY JOURNAL OF SCIENCE. Curators- Experiments with Frozen Dynamite.-Some interesting experiments were recently made at the works of the British Dynamite Company at Stevenston, Ayrshire, with the view of proving that dynamite in a frozen state is as safe to handle and to transport as in an unfrozen state. Professors James Thomson and Bottomley, of the University of Glasgow, were present. In the first experiment several cartridges in a frozen state, and in some parts beginning to thaw, were thrown one by one from the hand, with great force, against an iron plate without explosion. In the second experiment, a block of iron, about 400 lbs. weight, was allowed to fall from a height of about 20 feet on a light wooden box containing 20 lbs. of dynamite cartridges in a frozen state, and with slight signs of incipient thawing in spots more exposed to the warmth of the air. The box was smashed, and the cartridges were crushed flat and pounded together, but there was no explosion. The crushed cartridges were next made up into two heaps to be exploded. The ordinary detonator shatters but does not explode the frozen dynamite. The explosion was therefore effected by inserting in each heap a small unfrozen cartridge, with the ordinary detonator inserted into it, and then firing this off by a Beckford fuse. The two heaps were exploded successively, and it is worthy of remark that the explosion of the first, though very violent, did not set the other off. The Nizam Diamond-The Diamond in India. By Captain VI. Certain Phases of Bird Life. By Charles C. Abbott, M.D. Notices of Scientific Works, Progress of the Various Sciences, &c. Chemical Technology, or Chemistry in its Vol. I., Parts 1 and 2, price 36s., with more than 400 Illustrations. facture. Vol. I., Part 3, price 338., with more than 300 Illustrations. Vol. I., Part 4, price 21s., 300 Illustrations. Vol. I., Part 5, price 368. Prussiate of Potash: Oxalic, Tartaric, and Citric Acids, and Appendices containing the latest information, and specifications relating to the materials described in Parts 3 and 4. BAILLIERE AND Co., 20, King William Street, Strand. ERNERS COLLEGE of CHEMISTRY.EXPERIMENTAL MILITARY and NAVAL SCIENCES, under the direction of Professor E. V. GARDNER, F.E.S., &c., of the late Royal Polytechnic Institution and the Royal Naval College. The Laboratory and Class Rooms are open from 11 to 5 a.m. and from 7 to 10 p.m.daily. British Association for the Advancement of Science. The following are the officers of the forty-sixth annual meeting of the British Association which will commence at Glasgow on Wednesday, September 6th, 1876:-President designate-Prof. Thos. Andrews, M.D., LL.D., F.R.S., Hon. F.R.S.E., in the place of Sir Robert BE Christison, Bart., who has resigned the Presidency in Vice-Presidents elect-His consequence of ill health. Grace the Duke of Argyll, K.T., F.R.S., &c.; the Lord Provost of Glasgow; Sir William Stirling Maxwell, Bart., M.A., M.P.; Prof. Sir William Thomson, D.C.L., F.R.S., &c.; Prof. Allen Thomson, M.D., LL.D., F.R.S., &c.; General SecreProf. A. C. Ramsay, LL.D., F.R.S., &c. taries-Capt. Douglas Galton, C.B., D.C.L., F.R.S., &c.; Dr. Michael Foster, F.R.S. Assistant General Secretary -George Griffith, M.A., F.C.S., &c. General Treasurer Prof. A. W. Williamson, Ph.D., F.R.S. Local Secre. taries-Dr. W. G. Blackie, F.R.G.S.; James Grahame; J. D. Marwick. Local Treasurers-Dr. Fergus; A. S. M'Clelland. The President of Section A (Mathematical and Physical Science) will be Prof. Sir Wm. Thomson, D.C.L., F.R.S.; of Section B (Chemical Science), Mr. W. H. Perkin, F.R.S. On Thursday evening, Sept. 7th, at 8 p.m., there will be a Soirée; on Friday evening, Sept. 8th, at 8.30 p.m., a Discourse; on Monday evening, Sept. 11th, at 8.30 p.m., a Discourse by Prof. Sir C. Wy. ville Thomson, F.R.S.; on Tuesday evening, Sept. 12th, at 8 p.m., a Soirée; on Wednesday, Sept. 13th, the concluding general meeting will be held at 2.30 p.m. Especial facilities for persons preparing for Government and other examinations. Private Pupils will find every convenience. Analyses, Assays, and Practical Investigations connected with Patents, &c., conducted. For prospectus, &c., apply to Prof. E V. G., 44, Berners-street, W MORRIS TANNENBAUM, 37, FITZROY STREET, offers Jewellers, Mineralogists, Lapidaries, and especially Collectors of Kare Cut Gems (which he possesses in all existing kinds), large Collections of Fine Hyacinths in all Colours, Clear Spanish Topazes, Blue and Yellow Amethysts, Jargon, Olivine, Fossils, Fine Collections of Shells, Thousands of Indian Pebbles. Polished Agates, &c., Starstones and Catseyes, Garnets, Cape, Rubies, Fine Slabs of Lapis Lazuli, Fine Emeralds in the Matrix, Fine Crystallised Rubies and Brazilian Topazes, and Thousands of Rare Opals. Specimens and for Cuttings. Orders effected to all parts of the world. M awson and Swan are now able to supply CROOKES'S RADIOMETER at 255. 11 and 15, Mosley Street, Newcastle-on-Tyne. CHEMICAL NEWS, July 21, 1876. Repulsion Resulting from Radiation. 23 THE CHEMICAL NEWS. that the residual gas was a non-conductor of an induction VOL. XXXIV. No. 869. ON REPULSION RESULTING FROM RADIATION. INFLUENCE OF THE RESIDUAL GAS.* (PRELIMINARY NOTICE.) By WILLIAM CROOKES, F.R.S., &c. I HAVE recently been engaged in experiments which are likely to throw much light on some obscure points in the theory of the repulsion resulting from radiation. In these I have been materially assisted by Prof. Stokes, both in original suggestions and in the mathematical formulæ necessary for the reduction of the results. Being prevented by other work from completing the experiments sufficiently to bring them before the Royal Society prior to the close of the session, I have thought that it might be of interest were I to publish a short abstract of the principal results I have obtained, reserving the details until they are ready to be brought forward in a more complete form. In the early days of this research, when it was found that no movement took place until the vacuum was so good as to be almost beyond the powers of an ordinary air-pump to produce, and that as the vacuum got more and more nearly absolute so the force increased in power, it was justifiable to assume that the action would still take place when the minute trace of residual gas which theoretical reasoning proved to be present was removed. The first and most obvious explanation therefore was that the repulsive force was directly due to radiation. Further consideration, however, showed that the very best vacuum which I had succeeded in producing might contain enough matter to offer considerable resistance to motion. I have already pointed out that in some experiments, where the rarefaction was pushed to a very high point, the torsion beam appeared to be swinging in a viscous fluid (194), and this at once led me to think that the repulsion caused by radiation was indirectly due to a difference of thermometric heat between the black and white surfaces of the moving body (195), and that it might be due to a secondary action on the residual gas. This instrument proved that, at a rarefaction so high current, there was enough matter present to produce motion, and therefore to offer resistance to motion. That this residual gas was something more than an accidental accompaniment of the phenomena was rendered probable by the observations of Dr. Schuster, as well as by my own experiments on the movement of the floating glass case of a radiometer when the arms are fixed by a magnet." My first endeavour was to get some experimental means of discriminating between the viscosity of the minute quantity of residual gas and the other retarding forces, such as the friction of the needle-point on the glass cup when working with a radiometer, or the torsion of the glass fibre when a torsion-apparatus was used. A glass bulb is blown on the end of a glass tube, to the upper part of which a glass stopper is accurately fitted by grinding. To the lower part of the stopper a fine glass fibre is cemented, and to the end of this is attached a thin oblong plate of pith, which hangs suspended in the centre of the globe: a mirror is attached to the pith bar, which enables its movement to be observed on a graduated scale. The stopper is well lubricated with the burnt india-rubber which I have already found so useful in similar cases (207). The instrument is held upright by clamps, and is connected to the pump by a long spiral tube. The stopper is fixed rigidly in respect to space, and an arrangement is made by which the bulb can be rotated through a small angle. The pith plate, with mirror, being suspended from the stopper, the rotation of the bulb can only cause a motion of the pith through the intervention of the enclosed air. Were there no viscosity of the air, the pith would not move; but if there be viscosity, the pith will turn in the same di rection as the bulb, though not to the same extent, and, after stopping the vessel, will oscillate backwards and forwards in decreasing arcs, presently setting in its old position relatively to space. On April 5, 1876, I exhibited, at the Soirée of the Royal Society, an instrument which proved the presence of residual gas in a radiometer which had been exhausted to a very high point of sensitiveness. A small piece of pith was suspended to one end of a cocoon fibre, the other end being attached to a fragment of steel. An external magnet held the steel to the inner side of the glass globe, the pith then hanging down like a pendulum, about a millimetre from the rotating vanes of the radiometer. By placing a candle at different distances off, any desired velocity, up to several hundreds per minute, could be imparted to the fly of the radiometer. Scarcely any movement of the pendulum was produced when the rotation was very rapid; but on removing the candle, and letting the rotation die out, at one particular velocity the pendulum set up a considerable movement. Prof. Stokes suggested (and, in fact, tried the experiment at the time) that the distance of the candle should be so adjusted that the permanent rate of rotation should be the critical one for synchronism corresponding to the rate at which one arm of the fly passed for each complete oscillation. In this way the pendulum was kept for some time swinging with regularity through a large arc. A Paper read before the Royal Society, June 15, 1876. It was suggested by Prof. Stokes that it would be de sirable to register not merely the amplitude of the first swing, but the readings of the first five swings or so. This would afford a good value of the logarithmic decrement (the decrement per swing of the logarithm of the amplitude of the arcs), which is the constant most desir. able to know. The logarithmic decrement will involve the viscosity of the glass fibre, but glass is so nearly perfectly elastic, and the fibre so very thin, that this will be practically insensible. According to Prof. Clerk Maxwell the viscosity of a gas should be independent of its density; and the experiments with this apparatus have shown that this is practically correct, as the logarithmic decrement of the arc of the oscillation (a constant which may be taken as defining the viscosity of the gas) only slightly diminishes up to as high an exhaustion as I can conveniently attain-higher, indeed, than is necessary to produce repulsion by radiation. I next endeavoured to measure, simultaneously with the logarithmic decrement of the arc of oscillation, the repulsive force produced by a candle at high degrees of exhaustion. The motion produced by the rotation of the bulb alone has the advantage of exhibiting palpably to the eye that there is a viscosity between the suspended body and the vessel; but once having ascertained that, and admitting that the logarithmic decrement of the arc of oscillation (when no candle is shining on the plate) is a measure of the viscosity, there is no further necessity to complicate the apparatus by having the ground and lubri cated stopper. A movement of the whole vessel bodily through a small arc is equally effective for getting this logarithmic decrement; and the absence of the stopper enables me to have the whole apparatus sealed up in glass, and I can therefore experiment at higher rarefactions than would be possible when a lubricated stopper is present. Proc. Roy. Soc., March 30, 1876. 24 Action of Sodium on Benzol. CHEMICAL NEWS, OF CERTAIN KINDS OF FILTERS ON ORGANIC SUBSTANCES. The apparatus, which is too complicated to describe | ON THE ACTION 1. The logarithmic decrement of the arc of oscillation 3. The appearance of the induction-spark between the I measures the viscosity; 2 enables me to calculate the force of radiation of the candle; and 3 enables me to form an idea of the progress of the vacuum, according as the interior of the tube becomes uniformly luminous, striated, luminous at the poles only, or black and nonconducting. The apparatus is also arranged so that I can try similar experiments with any vapour or gas. The following are some of the most important results which this apparatus has as yet yielded :— Up to an exhaustion at which the gauge and barometer are sensibly level there is not much variation in the viscosity of the internal gas (dry atmospheric air). Upon now continuing to exhaust, the force of radiation commences to be apparent, the viscosity remaining about the same. The viscosity next commences to diminish, the force of radiation increasing. After long-continued exhaustion the force of radiation approaches a maximum, but the viscosity measured by the logarithmic decrement begins to fall off, the decrease being rather sudden after it has once commenced. Lastly, some time after the logarithmic decrement has commenced to fall off, and when it is about one-fourth of what it was at the commencement, the force of radiation diminishes. At the highest exhaustion I have yet been able to work at, the logarithmic decrement is about onetwentieth of its original amount, and the force of repulsion has sunk to a little less than one-half of the maxi mum. The attenuation has now become so excessive that we are no longer at liberty to treat the number of gaseous molecules present in the apparatus as practically infinite; and, according to Prof. Clerk Maxwell's theory, the mean length of path of the molecules between their collisions is no longer very small compared with the dimensions of the apparatus. The degree of exhaustion at which an inductioncurrent will not pass is far below the extreme exhaustions at which the logarithmic decrement falls rapidly. The force of radiation does not act suddenly, but takes an appreciable time to attain its maximum; thus proving, as Prof. Stokes has pointed out, that the force is not due to radiation directly, but indirectly. In a radiometer exhausted to a very high degree of sensitiveness, the viscosity of the residual gas is almost as great as if it were at the atmospheric pressure. With other gases than air the phenomena are different in degree, although similar in kind. Aqueous vapour, for instance, retarding the force of repulsion to a great extent, and carbonic acid acting in a similar though less degree. The evidence afforded by the experiments of which this is a br ef abstract is to my mind so strong as almost to amount to conviction that the repulsion resulting from radiation is due to an action of thermometric heat between the surface of the moving body and the case of the instrument, through the intervention of the residual gas. This explanation of its action is in accordance with recent speculations as to the ultimate constitution of matter, and the dynamical theory of gases. PART IV. By J. ALFRED WANKLYN. IN continuing my investigation I have experimented on a solution of strychnine. In 10 litres of London Thames water (West Middlesex Company), which yielded 0'05 m.grm. of albuminoid ammonia per litre, I dissolved 1263 grms. of strychnine, using a little hydrochloric acid (about 5 c.c. of the strong acid) to facilitate the solution. As will be seen, this solution contains o'1263 grm. of strychnine per litre, or 8.841 grains per gallon. Such a solution is bitter to the taste. I drank 5 c.c. of it, and found it to be very bitter. Submitted to the "ammonia process' "the solution yielded 5.20 m.grms. of albuminoid ammonia per litre. In making the experiment on the filtration of this solution I desired to ascertain whether or not the silicated carbon filter preserves its power, and accordingly employed the same filter which had already absorbed quinine and morphia in previous experiments. Already the filter had taken up about o'7 grm. of acid sulphate of quinine and 13 grms. of hydrochlorate of morphia, and since taking up these alkaloids had not had very large quantities of water passed through it. The filter was very carefully drained of water, and then the 10 litres of the above-described solution of strychnine placed in it. The first 5 litres of filtrate were thrown away, and the remain der was collected. nine. Submitted to the ammonia process it yielded some free ammonia and o'04 m.grm. of albuminoid ammonia per litre, which shows that the filtrate was devoid of strychI have sufficient confidence in the ammonia process to wager my life on the correctness of the results, and I drank 300 c.c. of the filtrate. It was not bitter, and I have not experienced any symptoms of poisoning with strychnine; and, as will be found on making the calculation, 300 c.c. of the unfiltered liquid contained about 40 m.grms. of strychnine, which is a poisonous dose. ACTION OF SODIUM ON BENZOL. I. SOME observers have stated* that when benzol is heated or digested with sodium it is decomposed or acted upon, but the nature of the product is not stated. Why potassium or sodium should act upon a comparatively inert substance like benzol is not, from theoretic grounds, very evident. To prove whether sodium has any action on C6H6 within a moderate range of temperature the following experiments have been made : Very pure benzol was prepared, by agitating the ordinary benzol with strong oil of vitriol for some days, washing with potassic hydrate, and distilling from water; it was then dried with calcic chloride, and rectified; after which it was further purified by several crystallisations, the crystals of benzol being pressed between (in a handscrew press) each operation, to separate any uncrystallisable hydrocarbon which might remain. This benzol boils constantly at 80.5° to 81°, and its vapour density and percentage composition, by combustion, agree very closely with the calculated numbers: 8 to 10 c.c. of this benzol, along with 1 to 15 grm. cleancut sodium, was introduced into strong tubes (about 15 inches long), the benzol warmed so that its vapour expelled the air from the tubes, which were then sealed and heated in an oil-bath to 150° C. for four hours, at the end * "Watts's Dictionary" (Benzene). CHEMICAL NEWS,} July 21, 1876. Development of the Chemical Arts. of which time a tube was examined, but the sodium, showed no further signs of action than fusion into globules. The remaining tubes were then heated to 200° to 250° C. for eighteen hours, when very little change was apparent, and the surfaces of the sodium having only a very slight brownish tint. On opening the tubes under mercury, no-or only a very minute quantity of-gas was found to have been produced, the mercury almost entirely filling the remainder of the tube not occupied by the liquid benzol. The benzol distilled entirely away between 80° to 81° without leaving any residue. Potassium in the presence of finely-divided silver had no more effect than the sodium alone. Zinc, or the copper-zinc couple, is also without action at temperatures up to 150° C. It was found unsafe to continue the action of sodium at temperatures much higher than 250° C., several violent explosions taking place, probably owing to the action of the fused sodium on the glass. II. If clean pieces of sodium or potassium be warmed under benzol in which phosphorus is dissolved, or pieces of sodium and phosphorus heated gently together under benzol, the surface of the metal becomes covered with a brilliant red film of amorphous phosphorus, which adheres very closely and prevents further action. The same action takes place in the cold, the film appearing at first yellow. It forms very rapidly on boiling, when the red substance on its first formation has the appearance of melting on the surface of the containing vessel. No metallic phosphide is formed at temperatures under 100° C., and the benzol is not affected. to By Dr. E. MYLIUS, of Ludwigshafen. Chorine and Chloride of Lime.-By far the larger portion of the hydrochloric acid evolved in Leblanc's soda process is utilised in the preparation of chlorine as an intermediate product in the manufacture of chloride of lime. As is well known the native peroxide of manganese (pyrolusite) has long been employed for this purpose. As long as this mineral was be found in sufficient quantity there was no occasion to seek out any substitute. By degrees the manganese mines became less productive, the samples in the market grew poorer in the effective ingredient, peroxide of manganese, and the prices became higher. Hence, on the one hand, experiments became necessary to re-convert the chloride of manganese-the residue from the production of chlorine-into peroxide, in order thus to reduce the outlay for maganese and to bring back a useless and troublesome residue into industrial circulation; on the other hand, attempts were made to produce chlorine without the intervention of manganese. The first procedure for the regeneration of manganese from its residues which has met with a practical application is that of Dunlop; the chloride of manganese being "Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzenends." 25 A decomposed by carbonate of lime, and steam at a pressure of from 2 to 4 atmospheres, and the carbonate of manganese thus formed being heated to 300° to 400° C. This procedure was carried out in the colossal establishment of Messrs. Tennant, at Glasgow, but has not been generally adopted among manufacturers of chlorine. It requires costly plant without accomplishing the required object-a perfect regeneration of the manganic oxide. An improvement on this process, although not industrially available, was that of Clemm* who substituted carbonate of magnesia for chalk. From the magnesium chloride formed by the decomposition of the manganese chloride he liberated hydrochloric acid by means of superheated steam, whilst the magnesia simultaneously formed was again applicable for the precipitation of fresh quantities of manganese solutions. This method, therefore, provided for the regeneration of the chlorine united with the manganese, which in Dunlop's original process was lost in the almost useless form of chloride of calcium. method of regenerating manganese, very advantageous under certain circumstances, has been devised by P. W. Hofmann, and has been successfully introduced in the works at Dieuze, and in certain German establishments. The inventor combines the regeneration of manganese in a successful manner with that of sulphur.t Hofmann precipitates the solution of manganese with the yellow polysulphides of calcium obtained by the lixiviation of vat-waste after prolonged exposure to the air. The manganese sulphide thus obtained, containing 57'5 per cent of sulphur, is burnt, a part of the sulphur being recovered as sulphurous acid and conducted into the chambers. The residue is heated with nitrate of soda (1 mol. to 1 atom of manganese in the residue), and thus converted into a higher oxide of manganese, which is then transferred to the chlorine stills as a manganese of 55 per cent. Oxides of nitrogen are evolved at the same time, which, with the aid of water and air, can be condensed as nitric acid. The peroxide thus obtained consumes, indeed, 2 to 3 per cent more hydrochloric acid than native manganese, but is much more readily soluble. Passing over other attempts at the same object, we may mention, as a curiosity, one process which proves, at least, how intense has been the desire to regenerate manganese. Esquiron and Gouin make the ingenious proposal to revivify manganese residues for the preparation of chlorine by means of chloride of lime! (To be continued.) ON MEASURING AIR IN MINES. ANEMOMETERS, or air-meters as they are often called, are * Clemm, Dingl Pol. Journ., clxxiii., 128. + Compare Dr. F. Tiemann's remarks on the utilisation of soda residues in a subsequent part of the present report. A Paper read before the Manchester Geological Society, 26 Measuring Air in Mines. CHEMICAL NEWS, Mr. William Peace, of Wigan, also patented an anemometer about twenty years ago, the moving power being from the action of air on a block of wood hung in the downcast shaft, from which, by means of a wire or cord, motion is given to a finger on a dial-plate above ground. The first anemometers which appear to have come into, Dr. Prestell, is described by Messrs. Negretti and Zambra, general use in mines were those of M. Charles Combes, of of London, in their illustrated catalogue for 1873. Paris, and Mr. Benjamin Biram, of Wentworh, Yorkshire, both being similar in principle to Mr. Elliott's. M. Combes, in his valuable work," Traité de l'Exploitation des Mines, 1844," refers to a description of his anemometer written by him in the Annales des Mines, by which it appears that his anemometer was introduced in 1837. Mr. Biram's anemometer, it seems by the patent specification, was sealed August 3, 1842, the scope of it being for registering the velocity of bodies propelled through water or wind and employment for paddle-wheels, stern-propellers, and other rotary engines. M. Combes's instruments seem to have been made by M. Newman, of Paris, and Mr. Biram's by Mr. Davis, of Derby. Robinson's anemometer, consisting of four revolving hemispherical hollow cups fixed on four arms radiating from a centre (as commonly used on observatories), have as yet been but little used in mines. It appears by F. Pastorelli and Co.'s work on standard instruments, and by other authorities, that this anemometer was invented by Dr. Robinson, of Armagh, and that it was used in tidal and meteorological observations on the coast of Ireland in 1850. It is also stated that Dr. Robinson, after a series of carefully conducted experiments, found that these cups fixed upon a vertical axis travel at the rate of one-third of that of the wind, and that this law exists irrespectively of the size of the cups or the length of the arms. Another combination of the windmill anemometer has recently come into use in mines. The arrangement is attributed to Dr. Parkes, F.R.S., for whom it is said to have been originally made by Mr. Lowndes, a working instrument maker in London. This instrument is some times known as the Casella or Casartelli anemometer. All windmill anemometers, it will be understood, require timing, and also correction, in order to ascertain the true velocity of the air from the number of revolu tions. Anemometers, 66 a mere inspection of which would enable an officer to ascertain in an instant the exact velocity of the air, without the necessity of timing or correcting,' have long been known, but the only one that I know of as being in use in mines, is the one devised by myself about twenty-five years ago, which is known as the Dickinson anemometer. By means of this the velocity of the air may be read off at a glance. It consists of a light, counterpoised, flat fanplate, which is usually made of talc, and hung upon two fine bearings, so as to be easily moved by the air current. Alongside of the fan-plate there is a quadrant, graduated and figured-the figure up to which the fan-plate is blown being the velocity of the air, in feet, per minute. There is also a spirit-level for setting the instrument level. In using this instrument all that is requisite to ascertain the number of cubic feet of air passing per minute is to multiply the velocity indicated by the anemometer into the area in feet of the place where the observation is taken. These anemometers have been made only by Mr. Casartelli, of Manchester. A modification of the Dickinson anemometer, which I have seen permanently fixed in the Bardsley Colliery, Ashton-under-Lyne, by Mr. George Wild, has the counterpoise made of a balance weight, which is worked by a chain over a pulley. For a fixture, like this, the chain and weight counterpoise appears to be an improvement, as the friction of the links of the chain over the pulley imparts steadiness to the fan-plate, and thus enables the average velocity to be better read in intermitting currents. About the same time as the introduction of the Dickinson anemometer, Mr. John Phillips, of Cornwall, devised a similar instrument, except that, as I understand, it had no counterpoise. M. Devillez has also introduced one on the same principle, but with a hollow cylindrical cup instead of the fan-plate. Another, with a flat plate suspended by two rods, by The foregoing anemometers are apparently the principal ones which have as yet been proposed for or actually used in mines. A variety of others, however, some of ancient date, have been used for measuring the wind on the surface. The first anemometer of which there appears to be any record is attributed to Dr. Croune, in 1667, which, it is said, did not answer the purpose intended. Better instruments seem to have been invented by other scientific men during the last century. The modes of action comprised the compression of a spiral spring, the elevation of a weight round a centre acting at the arm of a variable lever, a bag of air communicating with a glass tube, in the form of a lengthened U, being sometimes substituted for the spring. An anemometer by Leslie depended on the principle that the cooling power of a current of air is equal to its velocity. Another instrument depended upon the evaporation of water, the quantity evaporated being proportional to the velocity of the wind, varying, however, one would suppose, according to the dryness of the wind. Wolfius's anemometer, as described by him in 1746, consisted of four sails similar to those of a windmill, but smaller, turning on an axis. On the axis is a perpetual screw, which turns a vertical cog-wheel round a second axis. To the second axis is attached a bar on which a weight is fixed, so that the sails cannot turn without moving round ths bar in a vertical circle. When the wind acts upon the sails the bar rises, and this continues until the increased leverage of the weight furnishes a counterpoise to the moving force of the wind. It also appears to have acted by winding up a weight. Regnier's anemometer indicated the pressure upon a dial-plate, the moving power being a flat wooden surface on which the air acted, pressing it into a box with springs and mechanism. The anemometers of Dr. Whewell and Mr. Osler are described in Sir W. Snow Harris's report to the British Association, in 1841-44. That of Dr. Whewell was by means of a windmill fly, which worked an intermediate train of wheels and caused the varying pressure to be marked on a fixed cylinder. Mr. Osler's traced the direction of the wind and its pressure on a given area, which was moved by clock mechanism. An invention by the Rev. W. Foster is also described as ingenious. Lind's anemometer, which is an inverted glass syphon in the form of a U, is described in the Philosophical Transactions, 1775. An improvement of this has been made by Sir W. Snow Harris, who, by reducing one of the limbs to the diameter of one-fourth of the tube which is open to the wind, and by making the first part of the scale horizontal, has greatly increased the delicacy of the instrument. He also put a plumb on it, and a light vane, to facilitate observation. As a water-gauge or manometer, the inverted glass syphon, known as Lind's anemometer, is identical with what is now commonly used in mines for measuring the pressure of air. The water-gauge introduced a few years ago by Mr. John Daglish, formerly of Hetton Colliery, Durham, is on the same principle. M. E. Péclet, in his valuable "Traité de la Chaleur, Paris, 1860," says, that in 1820, M. Kallsténius employed a mill with twelve wands to measure the force of the air, and he describes M. Combes's anemometer. He also refers to a novel one by M. Morin, somewhat the same as M. Combes's. Also to the apparatus by M. Van Hecke, by which the ventilation is registered. Likewise to other instruments; in one instance by means of the air acting upon the surface of a body attached to one end of an arm working over a centre, there being a pointer at the other |