recently made by Mr. Wanklyn, at the Society of Medical Officers of Health, one of which concerned the purification of water supposed to contain the germs of typhoid fever. The following quotation from Dr. Tripe's letter will fully explain his position and that of Mr. Wanklyn :—“ I attended the meeting, but arrived too late to hear Mr. Wanklyn's speech; but was informed that he had stated that the non-detection of albuminoid matter, by Nessler's test, after distillation of filtered water with an alkaline permanganate, was strong proof of the absence of typhoid germs. The issue thus taken is one of the greatest importance, because if Mr. Wanklyn's statement be true, the most polluted water can be rendered potable and innocuous by filtration through a moderately thick bed of filtering materials. Certainly this statement is contrary to the opinions held by most other chemists, and if it be based on the absence of ammonia after distillation of the suspected water with an alkaline permanganate, the assumption is almost certainly erroneous, as Mr. Wanklyn himself admits that all the albuminoid matters are not converted into ammonia by his process. He would appear to have made this statement without knowing the size of the minute organisms which are suspected to be typhoid germs, otherwise he could not have placed any reliance on the Nessler test. Dr. Klein says that they are one-third the size of the blood corpuscles of man, but his engravings show them to be much smaller, and to possess only about one-sixth the area of a blood-disc. Now if they are similar to bacteria in their mode and rapidity of increase, it would be only necessary for a very few to obtain admission into the human body to set up their specific action, provided the person were susceptible to their influence. Does Mr. Wanklyn say that he could detect by the albuminoid ammonia process a dozen of these, which are less than the total bulk of one blood corpuscle, in half-a-pint of water? and if not, where is his argument?'

METALLURGY, MINERALOGY, AND MINING.

Compressed Peat.-"Silliman's American Journal" states that peat pressed into blocks and made so compact that a cubic foot weighs 85 to 100 pounds, is manufactured by Mr. A. E. Barthel, of Detroit, Michigan, and sells for one and a half dollars per ton.

The New Meta! Gallium.-At a meeting of the French Academy the Secretary opened a sealed note deposited by M. Lecocq de Boisbaudran, the first paragraph of which reads thus:-"Day before yesterday, on Friday, the 27th of August, 1875, between three and four o'clock in the afternoon, I obtained indications of the probable existence of a new simple body among the products of the chemical examination of a blende coming from the mine of Pierrefitte, valley of Argeles, Pyrenees." The evidence relied on to prove this discovery, a part of which evidence was given in the sealed note and another part in a note read at the same meeting, is: (1) the oxide (or perhaps a basic salt) is precipitated slowly by metallic zinc in a solution containing chlorides and sulphates; (2) its salts are easily precipitated by barium carbonate in the cold; and (3) it gives a spectrum showing two

violet lines of wave lengths 417 and 404 respectively. In all its other chemical reactions it closely resembles zinc; though in the precipitations it has always the preference when these are incomplete. To the metal thus indicated, Lecocq de Boisbaudran gave the name "Gallium." In a more recent paper he gives additional facts regarding the new metal, which he has been able to free almost entirely from zinc.

METEOROLOGY.

The great Iowa Meteor.-An account of this very large stone is given by the "Boston Journal of Chemistry," in the following terms:-"Some time ago a meteor of extraordinary splendour appeared in the heavens, over the State of Iowa, and after dazzling the eyes of all those who were so fortunate as to see it, burst asunder with a loud report, and in a few seconds disappeared. Fragments of this meteoric mass were scattered over a wide extent of country, and more than 700 pounds have up to the present date been picked up by various persons, and sold to geologists, chemists, and others, at high prices. We are under great obligations to C. W. Irish, Esq., civil engineer, of Iowa City, for a splendid specimen of the stone, which he kindly sent to us last autunın. The specimen weighs about 11 ounces, and accompanying it was a small fragment, which was sent for chemical examination. Our time has been so occupied that we have not been able to bestow upon it analytical labour, but intend shortly to do so. We presume, however, that it does not differ essentially from the specimens examined by Professor Henrichs, and we present in tabular form his results:

The stone, in physical appearance, resembles in most respects those which have fallen upon other parts of our planet, but in chemical composition it varies essentially. It is covered with a black crust, formed during the cosmical part of its motion through the earth's atmosphere. This crust, in the view of Professor Henrichs, is not due to fusion, but simply to the heating of the outer layer of the stone to a red heat. The interior is of a greyish colour, and resembles iron stones of terrestrial origin; when exposed to a red-heat the colour is changed to a black like the crust."

A Chronicle of the recent Falls of Meteorites is given in the "Academy,” May 13. On Sept. 14, 1875, at 4 P.M., a meteorite fell at Supino, in the district of Frosinone, Italy, of which Keller publishes a short notice in the "Opinione," Sept. 28, 1875. Its descent was accompanied with the hissing noise and explosion usually observed on such occasions. It is stated that the meteorite took an almost horizontal direction towards a house situated in Supino, which, owing to its having a parapet pierced with apertures, it passed without impact, and that it was then lost to sight. Fragments, respectively weighing 364, 199, 29, and 18.5 grammes, were afterwards found. After the lapse of more than 40 years (if we except the curious explosion which took place over Writtle, near Chelmsford, on Sept. 7, 1875, and that over Bradford, on Sept. 15, 1875, when no meteorites were found) a meteorite appears to have fallen in England on the 20th of last month, at Crudgington, near Wellington, Salop, at 3.40 P.M. It penetrated the earth to the depth of 18 inches, and is stated to weigh 73 lbs. It was exhibited last week, at a meeting of the Birmingham Natural History Society, when a resolution was passed that the meteorite should become the property of the nation, and be submitted to the fullest scientific investigation.

MICROSCOPY.

The Early History of Microscopy.-Dr. H. A. Hagen has a paper in the "American Naturalist" (March, 1876) which, while dealing with a kindred subject, alludes to this. He says it is well known that magnifying-glasses have been found among the Assyrian relics and the ruins of Pompeii, but the use of their magnifying power is nowhere recorded, though it is probable that some of the admirable gems of the ancients were cut with the help of lenses. Spectacles, perhaps in some way known in Rome, and even used by Nero, are said to have been invented at the end of the thirteenth century in Italy. Magnifying-glasses were manufactured by Arabians, and later by Roger Bacon, but certainly not used for the purposes of natural history before the beginning of the seventeenth century. Italy and Holland dispute the honour of the invention, which was perhaps simultaneous in the two countries. The great advantages of lenses for observation were directly acknowledged, and even augmented, by the invention of the compound microscope. Fontana in Rome and Drebbel in Holland are the rival inventors.

Microscopical Papers for the Quarter.-The following is a list of the several papers relating to microscopy that have appeared in the "Monthly Microscopical Journal" for April, May, and June:

On a New Arrangement for Illuminating and Centering with High Powers. By Rev. W. H. Dallinger, V.P.R.M.S.-The Identification of Liquid Carbonic Acid in Mineral Cavities. By Walter Noel Hartley, F.C.S. (King's College, London).-On some Structures in Obsidian, Perlite, and Leucite. By Frank Rutley, F.G.S. (H.M. Geological Survey). On the Aperture of Object-glasses. By F. H. Wenham.— On Zeiss'th Immersion. By W. J. Hickie, M.A.-Notes on the

Markings of Navicula rhomboides. By Dr. J. J. Woodward, U. S. Army. Some Results of a Microscopical Study of the Belgian Plutonic Rocks. By A. Rénard, S. J.-A New Microscopic Slide. By M. Ernest Vanden Broeck.-Measurements of Möller's DiatomaceenProbe-Platten. By Edward W. Morley, Hudson, Ohio, U. S. A.—On the Markings of the Body-scale of the English Gnat and the American Mosquito. By Dr. J. J. Woodward, U. S. Army.-Notes on Microphotography. By Surgeon-Major Edward J. Gayer, H.M. Indian Army, now Professor of Surgery, Medical College, Calcutta.-On Renulia Sorbyana. By J. F. Blake, F.G.S.-Remarks on Frustulia Saxonica, Navicula rhomboides, and Navicula crassinervis. By Charles Stodder, U. S. A.-On the Measurement of the Angular Aperture of Object-glasses. By Jabez Hogg, Surgeon to the Royal Westminster Ophthalmic Hospital, F.R.M.S., &c.

PHYSICS.

The Waves as a Motive Power.-Mr. B. Tower, who some time since described his method to an English audience, does not appear to have gone on in furtherance of his discovery. His machine consists in principle of a weight supported on a spring, so that it can oscillate on the spring through a considerable range in a vertical line. The scale of the spring, and consequently the natural period of oscillation of the weight, can be varied at will. When it is so adjusted that it synchronizes with the waves, the oscillations become very violent, and a large amount of power can be obtained from them. In practice, the springs consist of highly-compressed air pressing on the rims of hydro-pneumatic cylinders, and the arrangement is such that the vessel containing the compressed air forms the moving weight. At the meeting referred to Mr. Tower exhibited a design of a machine for working an auxiliary propeller of a sailing ship of 1,800 tons displacement. The moving weight in this case is 200 tons, and he showed by calculation that it would give about 30 horse-power in the long swell met with in the tropical calms, 260 horse-power in average ocean waves, and more than 600 horse-power in a heavy head sea. The space occupied by the machine compares favourably with a steam-engine of the same power. He also exhibited a model of the machine, which recently, in a moderate sea, had yielded power at the rate of 14 horse-power per ton of moving weight.

Experiments on the Periodic Waves of the Swiss Lakes.-At a recent meeting of the Physical Society of London (May 27), Professor Forel, of Morges, Switzerland, gave, in French, an account of some interesting experiments which he has recently made on the periodic waves which take place on the Swiss lakes, and are there called "Seiches." It was long since observed that the waters of most of these lakes are subject to a more or less regular rise and fall, which at times have been found to be as much as one or two mètres. M. Forel has studied this phenomenon in nine different lakes, and finds that it varies with the length and depth of the lake, and

that the waves are in every way analogous to those already studied by Professor Guthrie in artificial troughs, and follow the laws which he has deduced from his experiments. Most of the experiments in Switzerland were made on the Lake of Geneva, but that of Neuchatel was found to be best fitted for the study of the subject, possessing, as it does, an extremely regular geometric form. The apparatus he employed was very sensitive to the motion of the water, being capable of registering the waves caused by a steam-boat half an hour after it had passed, and five minutes before its arrival; and was so constructed as to eliminate the effect of common waves, and to register the motion, side by side, with a record of the state of the barometer, on paper kept in continuous motion. While he found the duration of waves to be ten minutes at Morges it was seventy minutes at Geneva, and this is explained by the narrowness of the neck of the lake at the latter place. This period he proved to be independent of the amplitude, and to be least in the shortest lakes. For shallow lakes the period is lengthened; and his observations show that the period is a function of the length and depth, and that longitudinal and transverse waves may co-exist, just as Professor Guthrie has shown to be the case in troughs.

Imitation Snow Crystals.-M. Dogiel, of St. Petersburg, selects a substance which crystallizes like snow, in a great variety of forms of the hexagonal system. And this substance is iodoform. To show the multiplicity of forms, M. Dogiel dissolves iodoform in boiling (90 per cent.) alcohol, and lets the solution cool in water of different temperatures. He gets mostly tabular crystals, when a solution containing 15 to 30 per cent. of iodoform is kept ten minutes in water of about 14° to 15° C.; whereas star-shaped and often very complicated crystals are had at temperatures of 26° to 37°. Some other modifications of the result are described by M. Dogiel, in a paper recently published, and he also gives drawings of the crystals he obtained.

A Remarkable Atmospheric Phenomenon at Ceylon.-The Rev. R. Abbay sent a communication on this subject to the Physical Society, May 27. In speaking of several of these phenomena he says that the most striking is witnessed from the summit of Adam's Peak, which is a mountain rising extremely abruptly from the low country to an elevation of 7,200 feet above the sea. The phenomenon referred to is seen at sunrise, and consists apparently of an elongated shadow of the mountain, projecting westward to a distance of about 70 miles. As the sun rises higher it rapidly approaches the mountain, and appears at the same time to rise above the observer in the form of a gigantic pyramid of shadow. Distant objects may be seen through it, so that it is not really a shadow on the land, but a veil of darkness between the peak and the low country. It continues to rapidly approach and rise until it seems to fall back upon the observer, like a ladder which has been reared beyond the vertical, and the next instant it is gone. Mr. Abbay suggests the following explanation of the phenomenon:-The average temperature at night in the low country during the dry season is between 70° and 80° F., and that at the summit of the peak is 30° or 40° F.; consequently, the low strata of air are much the less dense, and an almost horizontal ray of light passing over the summit must be refracted upwards and suffer total internal reflection, as in an ordinary mirage. On this supposition the veil