like tribe, or the curved-beak tribe, shape, form, size, is everything for their peculiar method of obtaining rations.

The Toucan feeds on insects, which lie deep in the corolla of flowers; it especially delights in tubular corollas, and has a great fondness for the rich, scarlet, fuschia-like clusters of the Rose de Monta, of Guayana. These clusters he seizes near the calyx, and by longitudinal movements of his powerful mandibles, aided by their serrated edges, saws them off, and then by his horny and fimbriated tongue, separates the insect portion from the vegetable, and swallows that which his palate approves of, like any other sensible bird. To see him hop from branch to branch, reach out his long, ponderous jaws, seize his breakfast, saw it off, as one sees a butcher in his stall, to see the parts rejected fall to the ground in petaliferous showers, and he maintain his equipoise, has been one of the most pleasant studies of my ornithological curriculum. I have made frequent post mortem examinations of his injestæ, and have always found the shields and remains of insects the most abundant in his craw.-R. P. STEVENS.

PHYSELLA NOT A FRESH-WATER SHELL. Mr. Tryon called the attention of the Conchological section of the Philadelphia Academy of Natural Sciences, to the curious error committed by several conchologists in treating Berendtia (Physella) Berendtii, as a fluviatile mollusk. He supposed that the resemblance of the first generic name given to Physa was the cause of the error. This Mexican snail has a Glandiniform shell and Mr. Tryon believed that its true position would be found to be near to Glandina. The Physella has been included as a fluviatile mollusk in Mr. Binney's monograph, recently published by the Smithsonian Institution, and still more recently in Mr. Dall's Classification of the Limnæidæ, published in the "Annals of the New York Lyceum of Natural History. Mr. Tryon also made some remarks upon the Darwinian Theory of the origin of species as illustrated by the "groups" or subgenera of Helices, established by Albers, and stated his conviction that nowhere in the animal kingdom could more conclusive evidences of the truth of Darwinianism be adduced.

GEOLOGY.

DID A GLACIER FLOW FROM LAKE HURON INTO LAKE ERIE? I find on page 193, of Vol. 4 of the AMERICAN NATURALIST, an article by Professor J. S. Newberry, on "The surface Geology of the basin of the great lakes and the valley of the Mississippi," which I wish to criticise as to the position taken by the Professor, that formerly a glacier flowed from Lake Huron into Lake Erie. On page 195 the Professor states that "Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario, are basins excavated in undisturbed sedimentary rocks. Of these, Lake Michigan is six hundred feet deep, with a surface level of five hundred and seventy-eight feet above tides; Lake Huron is five hundred feet deep, with a surface

level of five hundred and seventy-four feet; Lake Erie is two hundred and four feet deep, with a surface level of five hundred and sixty-five feet; Lake Ontario is four hundred and fifty feet deep, with a surface level of two hundred and thirty-four feet above the sea." "An old, excavated, now filled channel, connects Lake Erie and Lake Huron." And on page 200 the Professor states as his deduction. "2d. That the courses of these ancient glaciers corresponded in a general way with the present channels of drainage. The direction of the glacial furrows proves that one of these ice rivers flowed from Lake Huron, along a channel now filled with drift, and known to be at least one hundred and fifty feet deep, into Lake Erie, which was then not a lake, but an excavated valley, into which the streams of Northern Ohio flowed, one hundred feet or more below the present lake level." It will be granted, no doubt, that a glacier occupies the bed, or lowest part of the valley through which it flows, and, that like water, it flows from a higher to a lower point of elevation, or in other words, that it flows down hill, instead of up hill. But if Professor Newberry's position, that formerly a glacier flowed from Lake Huron into Lake Erie, be correct, then it must, in passing from the bed of Lake Huron into that of Lake Erie, have ascended a vertical height of two hundred and seventy-eight feet, for from the Professor's own showing the bed of Lake Erie is that number of feet above that of Lake Huron; for he states that the surface of Lake Huron is five hundred and seventyfour feet above the sea level, and that it is five hundred feet deep, which would make its bed seventy-four feet above the sea level; and he further states that the surface of Lake Erie is five hundred and sixty-five feet above the sea level and is two hundred and four feet deep, which locates its bed at three hundred and sixty-one feet above the sea level, and two hundred and eighty-seven feet above that of Lake Huron. If it be true, which is granted, as stated, that "an old, excavated, now filled channel connects Lake Erie and Lake Huron, then must it also be true, granting that the beds of these lakes occupied the same relative position to each other in the glacial period that they now do, that whatever glaciers flowed through it must have flowed from Lake Erie in the direction of Lake Huron, and found an outlet in that direction, instead of from "near the eastern extremity of Lake Erie into Lake Ontario; otherwise we shall have the phenomenon of a column of ice two hundred and fifty miles in length, by about twenty-five miles in width, saying nothing as to its thickness, lifting itself, by the mere force of gravity, from a lower up to a higher plane of elevation, which would appear to be impossible. The probabilities are that the furrows in the "old, excavated, now filled channel, connecting Lakes Erie and Huron," were made by running or floating icebergs, long ages after the work of excavating the beds of the great lakes by the glaciers had been completed, and not by true glacial ice. The difficulty of reconciling the observed facts in the case, seems to accrue from allotting too short a space of time to the glacial period. It would appear more perspicuous to allow an excavating period, corres

ponding in time with the period of the greatest continental elevation, during which period the glaciers would naturally flow in the direction of the lowest plane of their excavations, finding their outlets accordingly. The work of excavation being completed, then comes a continental subsidence, the "lower drift period," during which the narrower channels of excavation are completely filled, and the larger ones partially. Then comes another continental elevation, not so great, however, as the first; this is the "old channel" period, during which the great lakes take form as such for the first time, and all those "old drift channels" were excavated by running water and floating icebergs. Then comes another continental subsidence, much greater than the first or "lower drift period;" this is the upper drift period, during which those "old channels" are completely filled, and the surface elevated above them from one to two hundred feet, and even more. Then comes another continental elevation, the beginning of the present status of appearances.-L. J. STROOP, Waxahachie, Ellis County, Texas.

MICROSCOPY.

AMERICAN MICROSCOPES. - The able refutation by your correspondent, C. S., in your issue of September, of the statements made by Dr. Hagen, with respect to American microscopes, cannot but have been read with gratification by all interested in the question. It is a fact much to be deplored, that in scientific questions- of all others- national vanity and prejudices should so far warp the judgment of otherwise very competent writers, as to drive them to the most obviously, to use Dr. Hagen's own mild epithet, "comical" conclusions.

Referring to German stands, for whose glorification Dr. Hagen seems to have written the papers in question, any one who, like myself, has had the opportunity of visiting the workshops of nearly all the most celebrated manufacturing opticians of Europe, will say that stands of continental manufacture, be they French or German, are sadly deflcient in those improvements and appliances constituting a first class working English or American instrument. From this statement I except neither Mertz of Munich, nor Hartnack of Paris. Nachet, from the latter city, is the only maker whose instruments, in any way approach the perfection of either English or American stands. This deficiency in appliances and working means, in continental instruments, will be readily understood, when I mention that when I remonstrated upon the deficiency of stage motion in his best first class stands, Hartnack answered me: "Well, I see that you go for those English or American instruments looking like a steam engine, with screws, levers, and milled heads in every direction; we do not believe in such toys here." As to the upright vertical model, it speaks for, or rather against itself, as anybody knows 79

AMER. NATURALIST, VOL. IV.

that has ever used one of them; and still it is, to this day, the favored pattern adopted by students throughout France and Germany.

About objectives and eye pieces, I have nothing to say in addition to what C. S. has so ably discussed in his paper; unless I venture to remind Dr. Hagen that the wonderful performance of one given glass in the hands of one observer, often proves an utter failure in the hands of another, though both acknowledged “adepts” in the use of the microscope. This undisputed fact should make one very careful before pronouncing ex cathedra upon the merits of objectives produced by artists of unquestioned ability. In connection with this last remark, allow me to state that I shall be most happy to show to Dr. Hagen the Surirella gemma and its markings, which he only saw dimly with a 1-10th inch objective of Tolles; to show him, with a 1-8th inch immersion lens of W. Wales, the "basket work," as we call the elongated hexagons of that fine test at the Bailey Club, as near to Hartnack's theoretical diagram, as it is practicable to accomplish in a microscope view of that diatom. This very same 1-8th inch glass failed completely to show any markings on the Surirella in the hands of Hartnack, who, after having shown me the faintest display of the lines in question with his No. 11-almost equal to the 1-15th of our makers-pronounced my poor 1-8th an "inferior glass," which, "as long as I lived, would never resolve the Surirella gemma." So much for hasty judgments. The determination of the abstract, as well as relative merits of objectives, must stand, in the opinion of all experienced microscopists, when one considers the many details of manipulation which cannot fail to influence their performance, as one of the most perplexing and difficult problems to settle in practical optics.

Although not having the right to claim thirty years experience in the use of the microscope, and although one of the most insignificant dilettantis in the realm of microscopy, I venture to bring to bear my humble testimony, and some little experience gained in long European peregrinations, in favor of the superiority of English and American instruments, for both their mechanical and optical excellence, over all continental productions in the same line, begging here to mention, that in my statements I am influenced by no national prejudices, as I do not belong by birth, to either of the two aforesaid nationalities; neither am I a member of the Boston Optical Association. -T. O., Cornwall Landing, Sept. 16, 1870.

WALES' LOW POWER OBJECTIVES.*- May I ask of you the favor of a few lines in reply to Mr. Bicknell's note in the NATURALIST for June last. Mr. Bicknell agrees with me in according to Mr. Wales' objectives the high rank to which they are undoubtedly entitled, but in some way seems to have overlooked what the communication was intended to set forth before the microscopic world. It was not that Mr. Wales' 4-10 had an amplification of two hundred and ten diameters, or that Mr. Wales' did or did not

*This reply, with a number of other articles, has been unavoidably postponed on account of the space devoted to the reports of the meeting of the American Association.-EDS.

underrate his lenses in the naming of them. The point really presented was, that lenses of such low power should do so much, there not being any great liability of material difference in the amplification present in objectives of such low power as 3-inch. No measurement of its power was given. Not so, however, in the case of the 4-10, for as is well known, and as Mr. Bicknell states, objectives of various makers rating the same, differ greatly in their magnifying power. And this again occurs, not only with the objectives of different makers, but even the objectives of the same maker differ, although rated the same, e. g. in R. & I. Beck's Catalogue, 1868, are advertised 1-4 inch objective (No. 234) magnifying power two hundred and ten, and on a succeeding page 1-4 inch objectives (No. 296) magnifying power one hundred and forty diameters. Therefore I gave the amplification used, and such being known, it would in reality be immaterial what the objective might be called. In fact the succeeding paragraph distinctly states "that with no equal power of Powell & Leland's of London, of Hartnack of Paris, of Tolles and Grunow of this country, or of Gundlach of Vienna, various objectives of each and all of which makers I have examined, have either I myself, or other microscopists of my acquaintance, been able to effect this."

I do not say with a 4-10 objective, for firstly, they all differ in their amounts of amplification, and secondly, neither Hartnack nor Gundlach thus denominate their objectives, but as usual with Continental makers, number them as 1, 2, 3, and so on. The word power, however, I thought could not be misunderstood, such equality of power being most easily attained by the use of the draw-tube.

That an objective magnifying two hundred and ten diameters when used in connection with a No. 1 or an A eye-piece, should resolve the Pleurosigna angulatum, mounted, not dry, but in balsam, and by direct light, instead of oblique, is what I wished to put on record, and such I think the generality of microscopists would infer on perusal of the article. As, however, Mr. Editor, Mr. Bicknell is of the opinion that I have made an error in my measurements of the amplification, and as the liability of error is less when the testimony of many witnesses are concurrent, I would state that not only have I myself remeasured the amplification present on the use of said objective in said resolution, but that I am permitted to use the names of Dr. Edward Curtis, formerly of the Army Medical Museum, Washington, D. C.; of Mr. Joseph W. Ward, the well known microscopist of this city; and of Mr. O. G. Mason, Photographer of Bellevue Hospital, names familiar to all microscopists in New York, in testimony of the correctness of said measurement.

As regards the second point raised, namely, the underrating of objectives by their various makers, it is, undoubtedly, the fact, not however I think from any intention to mislead, but rather from an inherent want or defect in the nomenclature in use. The denominating of an objective a 4-10, 1-5, 1-8 and so on, answers a certain purpose of informing us of about what power is meant, but if, in addition, the makers would engrave