gypsum, placed in a solution of arseniate of ammonia, has been converted into arseniate of lime. With a solution of aluminate of potassa and gypsum, the result is the formation of glauberite (double sulphate of lime and potassa, the latter substituted for the soda in the mineral just named). Pieces of galena, kept for twenty years in a solution of bicarbonate of potassa, have yielded well-defined crystallised carbonate of lead. When pieces of limestone were immersed into a solution of plombite of potassa (solution of oxide of lead in caustic potassa), the result was the formation of beautifully-crystallised hydrated carbonate of lead; malachite has been obtained by the action of limestone upon nitrate of copper, converting it into subnitrate, which, in its turn, is converted into malachite by bicarbonate of soda.

The Teaching of Elementary Chemistry.-At the meeting of the British Association (Brighton), Dr. Wood read a paper on this subject. The sum and substance of his communication was that, in his experience, it was impossible to teach practical chemistry successfully in towns or places where there were no regular laboratories, and he strongly advocated the public appointment of such laboratories, where boys could be sent to gain the necessary knowledge. His opinion was that the recognised public examinations in chemistry were too difficult, that the standard was too high for young boys. Dr. Wood also proposed that the several great examining boards shall agree to use a common standard for elementary examinations, and should rigidly adhere to the conspectus. A very full discussion took place, in which some valuable suggestions were made by Professors Williamson, Lemoine, Barrett, and others engaged in the public teaching of chemistry. The president, in summing up the discussion, alluded to the great importance of teaching chemistry to every educated individual, and furthermore called the attention of the Section to the opening address of Dr. B. Sanderson in Section D, who had given a very high opinion of the necessity of chemical knowledge to everyone, irrespective of their calling.

A new Vegetable Ink.-In "Les Mondes," July 4, the editor states, that experiments are being made to acclimatise in Europe the Coriaria thymifolia, or ink-plant of New Grenada. The juice of this plant, locally termed chanchi, is at first of a somewhat reddish colour, but becomes intensely black in a few hours. This juice can be used for writing without requiring any further preparations; it corrodes steel pens less than ordinary ink, and has, moreover, the advantage of better resisting chemical agents. When the portion of America named above was under Spanish dominion, all public documents were written with chanchi, which was not removed from paper by sea-water.

On Meteoric Iron.-At the British Association, Prof. Mallett, U.S.A., exhibited three specimens of iron from Augusta, co. Virginia. One had been cut from the original mass by a planing machine, and without further preparation had been forged into a tolerably perfect blade for a paper-knife; another had been heated to redness in a vacuous porcelain tube (for the purpose of examining the occluded gases), and had then been with great difficulty forged into a blade of similar kind, in which cracks and flaws were visible. The third had been heated in like manner in vacuo, but to a

white heat, and this specimen could not be forged at all. The conceivable causes of this difference were briefly discussed, such as the more or less complete removal of the occluded gases, changed state of combination of the phosphorus and sulphur, and melting out of phosphide of iron, leaving the metal porous.

The Decomposition of Water.-A paper was read at the British Association, "On the Mutual Helpfulness of Chemical Affinity, Heat and Electricity, in producing the Decomposition of Water," by Dr. Gladstone and Mr. A. Tribe. Some metals are able of themselves to displace the hydrogen of pure water, while other metals are unable. Zinc, if perfectly pure, is incapable of doing so; but if it be brought into contact with another metal still further removed from the power of effecting the decomposition of water, the electric force started by contact of the metals enhances the chemical affinity sufficiently to make it effective—or, otherwise expressed, the electrical tension, plus the chemical tension, upsets the state of equilibrium between the oxygen and the hydrogen. The amount of action may be measured by a Thompson's galvanometer. The effect of varying the distance of two plates of zinc and copper was tried, and it was found that the chemical action increased slowly till the plates are within an inch or so of each other, but on continuing to bring them together the action increases at a rapidly accelerating ratio. Heat assists the action considerably. Magnesium is capable by itself of decomposing water, but its action is greatly increased by touching it with a piece of copper, and some of the hydrogen gas makes its appearance on the copper. If, instead of magnesium, a metal less capable than zinc of decomposing water be used, there is still found a deflection of the galvanometer, if it be united with a metal still more negative. The order for pure water seems to be-platinum, silver, copper, iron, tin, lead, zinc, magnesium.

The Quality of the Metropolitan Gas.-Dr. Letheby, the chief Gas Examiner appointed by the Board of Trade, has recently reported to the Corporation of the City, and to the Metropolitan Board of Works, on the quality of the gas supplied to the metropolis by the Chartered, the Imperial, and the South Metropolitan Gas Companies, during the last three months; from which it appears that the illuminating power has never been less than that required by the Act of Parliament. The common gas of the Chartered Company has ranged from an average power of 16.89 standard sperm candles at the Millbank testing-place, to 17.85 candles at the testing-place at Mile End. The Imperial Company's gas has ranged from 15.72 candles at Camden Street, to 16-85 at Oakley Square, Chelsea; and the gas of the South Metropolitan Company has averaged 15.78 candles. The cannel gas of the Chartered Company has had an average illuminating power of 25.74 candles at Millbank Street, and 26.06 candles at Arundel Street in the Haymarket. With respect to purity, Dr. Letheby reports that the gas at each of the testing-places has been constantly free from sulphuretted hydrogen, but that the fluctuation in the amounts of sulphur have been considerable, as from a minimum of 2.2 grains per 100 cubic feet of gas at Mile End, to a maximum of over 40 grains at Beckton, at Cannon Street, at Arundel Street, and at Hill Street, Peckham; the average proportions at the different testingplaces having been as follows:-The common gas of the Chartered Company

at Beckton, 26-98 grains per 100 cubic feet; at Cannon Street 25 77, grains; at Friendly place, Mile End, 8.71 grains; at Arundel Street, Haymarket, 18.89 grains; and at Millbank Street, Westminster, 26.96 grains; while that of the Imperial Company has been 32-98 grains at Oakley Square, Chelsea; 28-16 grains at Camden Street, Camden Town; and 25·71 grains at Graham Street, Dalston. The average amount of sulphur in the South Metropolitan gas was 36.05 grains per 100 cubic feet. It is a noticeable fact that the quantity of sulphur in the gas of the Chartered Company at Friendly Place has only once contained as much as 20 grains per 100 feet; and that during the last month the gas at Beckton, at Cannon Street, at Friendly Place, and at Arundel Street, has never contained 20 grains per 100 feet; the average for the month having been from 4.63 grains at Friendly Place to 13-64 grains at Beckton. Dr. Letheby regards this as highly satisfactory. The proportion of ammonia in the gas has not at any time or place exceeded the quantity (2-5 grains per 100 cubic feet) prescribed by the referees; the average amount being from nil to 1.28 grains per 100 feet. The Chemical News, July 19.

GEOLOGY AND PALEONTOLOGY.

Part V.

The Palæontographical Society Volume for 1871, which has only been a few months issued, contains the following important monographs :-1. "The Flora of the Carboniferous Strata." Part III. By E. W. Binney, F.R.S., F.G.S. Pp. 63-96. Pl. xiii.-xviii. 2. "The Fossil Merostomata." Part III. By Henry Woodward, F.G.S., &c. Pp. 71-120. Pl. xvi.-xx. 3. "Supplement to the Crag Mollusca." Part I. By Searles V. Wood, F.G.S. Pp. 1-90. Pl. i.-vii. Together with an "Introductory Outline of the Geology of the same District," with a Map, by S. V. Wood, jun., F.G.S., and F. W. Harmer, F.G.S., pp. i.-xxxi. 4. "Supplement to the Reptilia of the Wealden." Part IV. By Prof. Owen, F.R.S. Pp. 1-15. Pl. i.-iii. 5. "The Pleistocene Mammalia." Part IV. By W. BoydDawkins, M.A., F.R.S., &c., and W. Ayshford Sanford, F.G.S. Pp. 177194. Pl. xxiv. and xxv. 6. "The Pleistocene Mammalia." By W. Boyd-Dawkins. M.A., F.G.S., &c. Pp. 1-30. Pl. i.-v. Geology at the British Association.-The Geological Section began its sittings with the Sixth Report on Fossil Crustacea, by Mr. H. Woodward, F.G.S., in which various newly-discovered species from the silurian, carboniferous, tertiary, and other rocks were minutely described. The next paper was of great importance, by the Rev. J. Gunn, on the Prospect of Finding Productive Coal Measures in Norfolk and Suffolk, with suggestions as to the places best adapted for experimental borings. The next paper was on the Genera Trimerella, Dinobolus, and Monomeralla, by Thos. Davidson, F.R.S., and Professor King. Mr. John Gunn read a paper on the possibility of finding Coal in Norfolk and Suffolk, with suggestions for an experimental boring. Hunstanton was recommended as the most likely spot where coal would be soonest reached. Professor Hull thought that if there were any places where the chances of finding coal were nil, it was in the eastern

counties. In this opinion Professor Phillips coincided. Mr. Godwin Austen, F.R.S., protested against discouraging a boring, and thought there might be a continuity over Norfolk of the great central coal-fields. He concluded a long address by expressing his opinion that eventually a considerable coal area would be worked beneath the secondary strata. A paper by Professor Rath was next read on a remarkable block of lava ejected by Vesuvius during the great eruption of April 1872, proving the formation of silicates by sublimation. Mr. Gwyn-Jeffreys, F.R.S., followed with some remarks on submarine explorations. Afterwards, Dr. Adams read a report on the Fossil Elephants of Malta; and Professor Boyd-Dawkins, F.R.S., a very interesting communication on the Physical Geography of the Mediterranean during the Pleistocene age. Mr. Charles Moore also read a valuable paper on the Presence of Naked Echinodermata in Oolitic and Liassic Beds; after which Mr. J. E. Lee noticed some veins or fissures in the Keuper-filled Rhætic Bone Bed at Goldcliff, in Monmouthshire. Dr. Sim's paper on Quartz Nodules in the Crystalline Schists of Perthshire was next in order. There were many others of importance read, but our space does not admit of giving them all.

Professor Nordenskiold's Expedition to Greenland.-Professor Nordenskïold himself gives an admirable description of his excursion in the "Geological Magazine" for August, and in the preceding and following numbers. The paper is too long for abstract, but should be read by all who are interested in the subject.

Our London Coal-fields as they may be almost termed, were again the subject of consideration at one of the excursions of the British Association. At the excursion to Battle Abbey, Mr. Prestwich, F.R.S., gave a most interesting address on the more theoretical subject. He showed that long before the formation of any member of the secondary formations, there had extended over North Europe an immense land surface, broken up, like that before them, into hills and dales. This area, on which the vegetation of the coal period grew, extended certainly from South Wales to Belgium. It was eventually submerged, and covered over with the later secondary strata. It was originally thought that the latter extended from Bath into France, and that it would be useless to bore through them for coal. But subsequent researches found that these rocks thinned out in the direction of London. They had to eliminate some of the members, so that this circumstance, and their general thinning out, caused geologists to expect that the primary rocks would be found at no great depth. This proved true, for under London the tertiary and chalk strata had been found at Kentish Town resting on the old red sandstone. In Herefordshire, again, the chalk reposed on beds of the same age. At Harwich, in a wellboring, the lower carboniferous rocks were reached, and at Calais, across the sea, the chalk was found lying on the mountain limestone. Thus, positive evidence of the extension of these ancient Paleozoic or primary rocks had been afforded. At Calais, they reached at a depth of 1,300 feet, at Harwich 1,100 feet, and at Kentish Town about the same depth. This furnished the hope that the primary rocks would be found elsewhere under the chalk at a similar depth. The question was, where to go and look for them? All their efforts were only tentative, and many experiments like

that before them would have to be carried out before they found out their way. But every step taken was so much ground gained. Mr. Prestwich then showed how the ancient carboniferous formation had been disturbed, and compared all those that lay in a certain direction. Thus, in Belgium, at the foot of the Ardennes, there was a patch of coal-measures forty or fifty miles long, and running in an east and west direction. In Somersetshire the range of hills had the same direction as those of the Ardennes. The coal basin at the latter place had the same strike as those of Bristol and South Wales. The elevation of these took place before the formation of the new red sandstone. The present surface elevation was no guide whatever to the disposition of the ancient rock. In Belgium the coal dipped beneath the chalk, and the question was what became of it? If the strike always followed the same line there would be no difficulty in answering this, but it did not follow a straight line, but was curved, as in the Ardennes Hills. Mr. Godwin Austen thought that the Ardennes chain passed underneath where they stood, but Mr. Prestwich slightly differed from this, and thought the strike and range of the coal-measures in the South Wales coalfield and that of Belgium extended farther north. This was not an experiment to find coal, as had been asserted, but simply a scientific experiment to determine the position of the primary rocks. With other similar borings it might be possible to discern the actual range of the older rocks, and find out whether coal was to be found in Herefordshire or Kent. Where this boring was going on, they might meet with the mountain limestone, but he did not think the actual coal-measures would be found. If they came on the silurian rocks, they must go farther north to search for coal, so that it greatly depended on what they came to underneath them as to whether they should continue.

MEDICAL SCIENCE.

The Coagulation of the Blood.-A short communication on this point was made by Mr. E. A Schafer to the British Association, detailing a variety of experiments, from which the following conclusions were drawn:-That frog's blood, especially if taken during the winter months, exhibits but very little tendency to coagulate, with the exception of the portion in immediate contact with a foreign surface; that when apparently coagulated throughout, the central portions are very apt to remain fluid, and to impart coagulability to the expressed serum; that the clot, when formed, frequently tends to attain a relatively very small bulk; and, finally, that this diminution in bulk is due to contraction merely-not reliquefaction of the fibrine..

Rythmical Variation of Arterial Pressure.-Professor Burdon Sanderson read a paper on this subject at the same meeting as above mentioned. He pointed out the rythmical irregularities observable in the pulsation of certain animals, stating that the periods of fast beating correspond to inspiration, and that the periods of slow beating correspond to expiration; and explaining how this is recorded by a graphic method. Discussing the question of the relation of these phenomena, he showed that, when the muscles are subjected to paralysis, so that respiration almost ceases, there is