the paper by Desor, than whom no one can speak with greater authority, in which he has made a comparison between the glacial marine beds of the North and the marine coast deposits of the Southern states, parallelizing the deposits in a masterly manner. His remarks entirely confirm the views given above. One difficulty Desor had in parallelizing the Laurentian beds of the North with those of the South containing the remains of land animals, was the apparent absence of the remains of land animals in the clays of the North, but since then teeth of the bison have been found at Gardiner, Maine, in the upper part of the clays. It may also result from farther investigation that the phosphate beds were laid down at a later period than we have supposed; at the time when the great mammals found in the cave at Phoenixville by Mr. Wheatley flourished, perhaps during the earlier portion of the river terrace period when the mammoth and mastodon lived both in the northern and southern states.

Thus, the parallelism between the Quaternary beds North and South would seem to be even more exact than Desor twenty years ago could make it with his data. The climate gradually grew warmer from Labrador to Florida; the Gulf Stream did not apparently change its bed during the Quaternary period; the oscillations of level of the coast of South Carolina were slight and involved but a few feet, where in Canada and Labrador the rise and fall involved several hundreds; and the denudation effected in the North by land ice, was caused in the South by oceanic currents, waves and atmospheric agencies. There are apparently no facts to show that while the glaciers lined the coast of New England, the waters of South Carolina were not as warm, if not warmer, than at the present day, from the effects of the Gulf Stream.Bulletin Essex Institute.

DEEP SEA EXPLORATIONS. The expedition by the Coast Survey, under the charge of Professor Agassiz and Count Pourtales, to explore the sea at great depths in the Southern Atlantic and along the Pacific coast, revives the interest in the remarkable discoveries made by the late English deep-sea dredging explorations in the Mediterranean Sea. It seems, as "Nature" remarks, that Humboldt, as long ago as 1812, maintained that

*Post Pliocene of the Southern states and its relation to the Laurentian of the North and the deposits of the valley of the Mississippi. By E. Desor. American Journal Science and Arts. 1852. Vol. 14. p. 49.

such a low temperature exists at great depths in tropical seas as can only be accounted for by the hypothesis of undercurrents from the Poles to the Equator. The temperature soundings taken on the last English expedition show that the bottom of the sea off Portugal, below one thousand fathoms, ranges from thirty-nine to thirty-five degrees, or about the freezing point. In the Mediterranean the temperature beneath the hot surface stratum of water is uniform to any depth-namely, about fifty-five degrees. It is naturally inferred that in the Atlantic and Pacific oceans an undercurrent of polar icy water is flowing southward under the warmer tropical waters; and this is sustained by the discovery at great depths of polar animals in the seas of Florida and Cuba. The English expedition under Professor Carpenter, the well known physiologist, has also detected the existence of an outward undercurrent in the Strait of Gibraltar, which carries back into the Atlantic the water of the Mediterranean that has undergone concentration by the excess of evaporation in its basin. Professor Carpenter confirms the theory previously urged by Captain Maury, that the cause of the superficial in-current and the deep out-current is to be found in the excess of evaporation, the Mediterranean water being from evaporation denser than the water of the Atlantic. Carpenter then compares the polar and equatorial areas, and shows that there is a tendency in the former to a lowering of level and increase of density, which places it in the same relation to the latter as the Mediterranean bears to the Atlantic.

COAL BEDS IN PANAMA.- In a paper read before the Geological Section of the British Association, Dr. Hume stated that, during a recent residence upon this isthmus, he learned that a series of seams of coal had been found in a secluded and primitive portion of the country, not far distant from the railway. He had procured and analyzed some specimens of the coal, and had found 75 per cent. of carbonaceous matter, the balance being water and ash, and a very small quantity of sulphur. The coal possessed a fair heating and large illuminating power.

MICROSCOPY.

ANGULAR APERTURE.- An anonymous querist in the "Monthly Microscopical Journal," incidentally to asking the aperture of a certain lens, urges the importance of angular aperture as an ele

ment in the construction and study of objectives, and intimates, which is hardly saying too much, that the peculiar qualities of the objectives depend more on their angular aperture than on their focal lengths. "Focus and aperture are in fact both essential factors in the denomination of an object-glass, and where a difference exists in either we must keep in mind that we are comparing different things, and not the same things with differing qualities." The estimation of any angular aperture, so well expressed by “B,” is perfectly familiar and undisputed among experienced microscopists, although its exact bearings are not always easily apprehended by beginners; and that microscopists need occasional caution in regard to it may be inferred from the case in point, where an accomplished writer stated an extraordinary performance of a lens without mentioning the range of its apertures or the aperture at which he worked it. The peculiar and entirely independent qualities of lenses of low and of high angles are everywhere understood alike; but the extent to which success has been attained in this country in the construction of high angles cannot be appreciated abroad when "B," evidently well informed on other points, would not be surprised to hear that a one-fifth of excessive resolving power had an angular aperture of 150° or 160°. Any one in this country would be "surprised" to hear that its highest angle was less than 170°.

Makers should always engrave the angular aperture upon the mounting and on the boxes of their objectives. The neatness and sufficiency of this plan, however, is marred in the case of many modern objectives whose screw-collar adjustment gives a wide range of powers and angles. Exactly at what point of adjustment the measurements should be made in these cases is one of the most difficult points to be settled in endeavoring to obtain a uniform nomenclature in regard to the works of different makers. At least for the present, until some standard degree of adjustment can be agreed upon, both the highest and lowest figures should be given where the range is considerable.

The

PASSAGE OF CORPUSCLES THROUGH THE BLOOD-VESSELS. "Monthly Microscopical Journal" reviews a paper on the subject read before the Royal Society by Dr. R. Norris. Previous hypotheses fall short in regard to the most singular and important part of the process. The question is less how the corpuscles get

out, than how they get out without leaving any trace of their passage through the wall. Observers are agreed that both red and white corpuscles pass out of the vessels through apertures which, manifest during the period of transit, can be seen neither before nor after that time, and that it is essential to the process that the corpuscles shall cohere to the wall of the vessel and shall be subsequently subjected to pressure from within. The physical conditions essential to the passage of a rigid body through a colloid film, as when a solid body passes through a soap-bubble without breaking it, are present in the case of the minute blood-vessels and the corpuscle, and are as follows;—an intimate power of cohesion, either mediately or immediately, between the film and the body, a certain amount of pressure from within, and cohesive plasticity of the substance of the film so that the breach in it may become united as it descends upon the opposite surface of the body which is being extruded.

CUTTING AND STAINING TISSUES. - Mr. E. Ray Lankaster recommends, in the "Quarterly Journal of Microscopical Science," that a small piece of tissue be enclosed in a metal box and frozen by means of a freezing mixture. It is then held between pieces of pith in wooden forceps (or an American clothes-peg) while sections are cut by a razor cooled in snow, the cutting being performed in a cold room. Three razors are used that two may be cooled while one is used. The sections are first placed in a one-half per cent. gold chloride solution, or in silver nitrate solution if desired. After five to seven minutes they are transferred to distilled water and soaked for a few hours. They are then placed in water acidulated with lactic acid to reduce the gold chloride, and after the redviolet color is fully developed they are teased out, if necessary, and mounted in glycerine.

ADULTERATION OF TEA AND COFFEE. According to Dr. Hector Helshan's paper on the employment of the Microscope in analysis, before the South London Microscopical and Natural History club, coffee drinkers are liable to be treated to a decoction of roasted coffee-berries, chicory, poor flour, stale sea-biscuit, tanyard refuse, peas, beans, and saw-dust. Some of these modern improvements may be escaped by buying the coffee unground. Dainty tea-drinkers will notice with interest that the Chinese export teas rendered attractive by the salts of copper, lead, and iron,

ens.

and cheapened by mixture with the refuse tea-leaves from the kitchOther leaves are largely prepared and sold as tea, and the process of improvement is further carried on by the importers at home. Willow leaves have been much substituted for tea, and have been said to be a good substitute.

ANOTHER ERECTOR.- A flat minor above the eye-piece was exhibited by Mr. E. Richards, as an erector for the microscope, at the October meeting of the Royal Microscopical Society. He uses a glass plate platinized in front. This little erector is cheap and easily used when the microscope is in a vertical position. It is not, however, easily applicable in an inclined position of the instrument; and it is liable to narrow the field of view. This is a modification and adaptation of Mr. E. T. Newton's apparatus published in the "Quarterly Journal of Microscopical Science," July,

1871.

AMERICAN MICROSCOPICAL SOCIETY OF THE CITY OF NEW YORK. Rooms: Mott Memorial Building, 64 Madison Av., New York. Officers: President, F. A. P. Barnard, S.T.D., LL.D.; First Vice President, J. E. Gavit; Second Vice President, H. G. Piffard, M.D; Recording Secretary, J. W. S. Arnold, A.M., M.D.; Corresponding Secretary, R. A. Williams, Jr., A.M.; Treasurer, E. C. Bogert; Curator, Samuel Jackson; Librarian, J. H. Cornell ; Trustees, T. F. Harrison, C. Van Bunt, W. H. Atkinson, M.D., D.D.S., S. G. Perry, D.D.S., D. H. Goodwillie, M.D., D.D.S. -The Medical Record.

IMPROVED APPARATUS FOR DRAWING WITH THE MICROSCOPE. Mr. E. T. Newton proposes, for microscopical drawing, a steel reflector partially covering the eye-lens and mounted with a provision for rotation, so as to be easily adjusted to use with the instrument inclined at any angle. The Beale neutral-tint reflector, etc., should be mounted, for those who prefer to use it, with a similar rotating movement. This substitute for the camera has the additional advantage of being an erecting arrangement.

MICRO-SPECTROSCOPE. Mr. H. G. Bridge states in the "Monthly Microscopical Journal" that it is perfectly feasible, with Mr. Browning's bright-line micrometer, to record or map the spectra observed, so that the positions given shall be correct to the unit of the micrometer circle.