The Metallurgy of Lead.-Mr. John Jex Long read the first part of a paper on this subject before the Glasgow Philosophical Society, March 25, 1872, in the course of which he described the operations which he had personally witnessed at the works of the London Lead Mining Company, at Middleton-in-Teesdale, a few miles from Barnard Castle, where the mining operations were commenced about 170 years ago. He explained the geological position of the lead-bearing rocks in Teesdale, describing the direction, extent, and richness of the mines, and their mode of occurrence in flats, pockets, strings, &c. The annual product of the mines referred to is about 2,000 tons of metallic lead, containing about 9 ozs. of silver per ton, which is separated in the metallic form by Pattinson's process. Before the company obtained any pecuniary return from the mines, they had to expend about 30,000. Mr. Long described his exploration of the Coldberry Mine at Middleton, the mode of working it, and the various mechanical operations by which the mineral is prepared for smelting; and he promised, on a subsequent occasion, to devote the second part of his paper to the consideration of the smelting and refining processes and the extraction of the silver. The paper was profusely illustrated by specimens.

Waste of Sulphur in Mining.─Dr. W. H. Tayler writes to the "Chemical News," May 24, upon this subject. He states that whilst minerals of every description are rising in value, it will scarcely be credited, although such is the fact, that in several of the tin mines in Cornwall, at the present time, a large source of what ought to produce wealth is allowed to be wasted. Large quantities of sulphurous fumes are allowed to pass off daily in calcining the tin stuff, instead of manufacturing it into sulphuric acid. He states that he knows of an instance where three tons of sulphur are daily allowed to escape, which if manufactured into sulphuric acid, the present price of which is 37. 10s. per ton, would yield a revenue of more than 12,000l. a year. While Spain and Portugal and other parts of Europe are ransacked to find sulphur ores to supply the manufacturers of sulphuric acid, in Cornwall all these sources of wealth are allowed to be wasted.

Crystalline Dissociation.—MM. Favre and Valson have published the second part of a very valuable monograph on this subject. It contains so large a series of tabulated forms, the results of experiments, that an abstract would be impossible.

MICROSCOPY.

Wenham's improved Reflex Illuminator for the highest powers of the Microscope. We cannot resist giving our space to this excellent invention of Mr. Wenham's for microscopic illumination. The diagram (p. 329), five times the size of the instrument, illustrates the plan he has adopted to overcome the defects of the olden apparatus. In this a is a cylinder of glass half an inch long and four-tenths in diameter, the lower convex surface of which is polished to a radius of four-tenths. The top is flat and polished. Starting from the bottom edge, the cylinder is worked off to a polished face at an angle of 64°: close beneath the cylinder is set a plano-convex lens of 14 focus. Parallel rays sent through the lens, after leaving the lower convex surface of the cylinder, would be refracted to the point shown by the

dotted lines if continued in solid glass; but by impinging on the inclined polished surface (which is far within the angle of total reflection) they are thrown on the flat segmental top; here they would be totally reflected and beaten down again to the point, b, outside the cylinder; but if an objectslide, c, be laid over the flat top with an intervening film of water, the rays proceed on till the focal point reaches the upper surface or is slightly · beyond it; here total reflexion now takes place; all the light is concentrated to a minute spot in the centre of the field of view of the microscope, and most of the rays are available for any object brought there by traversing the slides over the water top of the illuminator, which must be kept full without allowing any to run down the reflecting surface. It will be seen, in order to get the focal point in the centre of the microscope, that the lens centre must be excentric; but this does not involve the slightest inconvenience, as the excentricity only amounts to a little over two-tenths of an inch, and is so small that the same adjustment of the mirror serves during an entire revolution. The apparatus rotates on the focus as a centre. The management of this illuminator is very easy and simple; its fitting goes into the ordinary sub-stage, and has an independent rotary movement of its own, like that of Nachet's prism. The cylinder is brought up nearly level with the stage. The centre of rotation is set true by a dot on the fitting, seen with a 13 object-glass. A drop of water is then placed on the top, upon which the slide is laid. The required objects on the slide are found by a low power, and may be distinguished by their brilliant appearance, while those on the cover are nearly invisible. The light is thrown up by either the plane or concave mirror. The former is generally the best and most controllable. The lamp should not be placed much beyond the stage, else its direct rays will get underneath and mar the blackness of the field. Having got the best effect, say on a diatom, or insect scale, by tilting the mirror, we now proceed to rotate the illuminator. During this the most exquisite unfolding of structure takes place, opening out as it were into detail the form of bosses or ribbings. On that superb test, the Podura, for example, when the light is thrown from the apex to the quill, the whole scale is dotted over with bright blue spots laying in a zigzag direction; these are the most prominent parts or the club-end of the markings, which are nearest in contact with the glass. Fuller details are contained in the. paper from which these remarks are taken, which should be referred to by the reader. Vide Monthly Microscopical Journal, June 1872.

The Best Way to see the Markings on Battledore Scales is the following, according to Dr. Anthony ("Monthly Microscopical Journal," June, 1872). He says that scales are best seen by "transmitted" ordinary light, when a "pin-hole" stop is placed like a small cap on the usual wide-angled condenser, and by being very particular that both flame of the lamp and object are in focus, or very nearly so, at the same time. When scales are looked at by "reflected" light, then they are to be seen at their best by bringing up a little transmitted light at the same time, such light being quite subordinate, and only for the purpose of rendering the black shadows transparent. A similar effect of course can be got by using a second lamp and "bull's-eye" at the other side of the microscope, or even in a minor degree by a bit of white card, placed in the stage beneath the object, so as to reflect light, but

on the whole he prefers the first form of "double illumination" as equally satisfactory and far less troublesome.

Mr. Collins' Light Corrector.-An ingenious bit of apparatus has been devised by Mr. Charles Collins (17, Great Portland Street). It consists of a brass stage-plate with a groove in which rotates a diaphragm of four apertures, one of them being open and the other containing blue glasses of special tint, and one with a finely-ground surface. These effectually correct the yellowness of all artificial illumination, making the light soft and agreeable to the eyesight as well as improving the definition. It is in fact an improvement on Rainey's Light Modifier so as to obtain more varied effects, and does not require any special fitting, as it can be used on any microscope.

A Curious Fact in Bichromatic Vision has been observed and described by Mr. J. W. Stephenson, F.R.M.S. He says, as of course is known to most students of optics, that, by the aid of a double-image prism and a film of selenite, two images may be shown in the field of the microscope, the colours of which will be complementary the one to the other, and that when these images overlap, the resulting image will be, as far as the overlapping extends, of white light; but it is not, he thinks, so well known that when, by a suitable arrangement, different colours are made to occupy the two fields of a binocular, the resultant is a combination of such colours, and that if these are complementary to one another, the sensation of colour induced in the brain by the retina of one eye, is neutralised by that which reaches it through the instrumentality of the other, and that by the combination of the two the sensation of colour is entirely lost. This, however, Mr. Stephenson observed in the most convincing way. The fact is a little curious, and we think, as yet, is insufficiently explained.-Monthly Microscopical Journal, May 1872.

The Two Best Test Objects.-Dr. Col. Woodward says that Amphipleura pellucida is a useful and valuable test for immersion objectives of th inch focal length or less. Lower powers can only hope to resolve it if possessed of excessive angular aperture. When, however, it is desired to discriminate between small differences in the excellence of objectives intended for the most exquisite resolution, a more subtle test is required, and this will be found in the nineteen-band plate of Nobert, by those who take proper precautions in its use. Those, however, who believe they have secured resolution whenever they see lines in the higher bands of the plate, without duly considering their number, must not be surprised if objectives they have accepted as resolving the ultimate bands of the plate fail to show the striæ on even the coarsest frustules of the Amphipleura pellucida.—Monthly Microscopical Journal, April.

PHYSICS.

Death of Professor Morse.-We regret being obliged to announce the death of Professor Samuel Finley Breeze Morse, which took place at his residence in New York city, on April 4, at the advanced age of eighty-one

years. Few Americans have attained so world-wide a renown as Mr. Morse, growing chiefly out of his success in devising and introducing the system of electric telegraphy which bears his name. Mr. Morse was the eldest son of Jedidiah Morse, D.D., an American clergyman, better known as a geographer, whose writings were the first devoted to the elucidation of American geography, his educational works of this character remaining for more than a generation in general use. Prof. Morse was born in Charlestown, Mass., April 27, 1791. He graduated at Yale College in 1810.

An Improvement in Barry's Singing Flame has been devised in America by Mr. W. E. Geyer, and is described by him in "Silliman's American Journal." He states that a simple addition to the apparatus described by Barry last year has given him a flame which, by slight regulation, may be made either: (1) a sensitive flame merely; that is, a flame which is depressed and rendered non-luminous by external noises, but which does not sing; (2) a continuously singing flame, not disturbed by outward noises; (3) a sensitive flame, which only sounds while disturbed; or (4) a flame that sings continuously, except when agitated by external sounds. The last two results, so far as is known to him, are novel. To produce them it is only necessary to cover Barry's flame with a moderately large tube, resting it loosely on the gauze. A luminous flame six to eight inches long is thus obtained, which is very sensitive, especially to high and sharp sounds. If now the gauze and tube be raised, the flame gradually shortens and appears less luminous, until at last it becomes violently agitated, and sings with a loud uniform tone, which may be maintained for any length of time. Under these conditions, external sounds have no effect upon it. The sensitive musical flame is produced by lowering the gauze, until the singing just ceases. It is in this position that the flame is most remarkable. At the slightest sharp sound, it instantly sings, continuing to do so as long as the disturbing cause exists, but stopping at once with it. So quick are the responses, that by rapping the time of a tune, or whistling or playing it, provided the tones are high enough, the flame faithfully sounds at every note. By slightly raising or lowering the jet, the flame can be made less or more sensitive, so that a hiss in any part of the room, the rattling of keys even in the pocket, turning on the water at the hydrant, folding up a piece of paper, or even moving the hand over the table, will excite the sound. On pronouncing the word "sensitive," it sings twice; and in general it will interrupt the speaker at almost every "s" or other hissing sound.

A new Seismograph has been described in a paper before the Wellington Philosophical Society, New Zealand, by Mr. Wm. Skey. The following is a partial account of the instrument. A small block of metal, having a thin slip of platina attached, or a small wire of this metal projecting a little apart from it horizontally, is connected with an electro-magnet with keeper suspended, and this with a single cell of a battery. A very fine silver wire (that used for sewing wounds), 3 ft. long or so, joined at its lower extremity by a little platina wire, depends from a point above, so that the two platina wires may intersect; a firm adjusting screw or other apparatus set contiguous to the point of suspension enables one to put this point in such a position that these wires are allowed to press but very slightly upon each other. The silver wire is connected with the other pole of the cell through