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—The outline figures below are given at the request of an amateur-microscopist, and represent a cheap condenser, which he has constructed for his own use, and now publishes in the hope that it may be useful to others. Having seen his own instrument, with the condenser, in operation, we were so well satisfied with the results, as willingly to accord him space for his explanation. The woodcuts are executed from drawings sent to us with the accompanying particulars:—

—A, spot-lens about -inch focus. B, achromatic spot-lens, about 1-inch focus, placed at about the same distance as in a Kelner eyepiece, in a tube C, screwed in a flat ring of metal D, which is supported on a flat plate G, secured by a holdfast E, allowing room between for a diaphragm F, to revolve freely on its axis, which is done by a screw passing through a holdfast into the plate G. H is a tube -inch long for carrying polariscope.

A, for direct light. B, for difficult test-objects. C, dark-ground illuminator. D, small aperture, with shutter E, having a small hole in it. The features presented by this condenser are,—that it is applicable for both high and low powers, can be used by merely sliding it into a tube under the stage, and never need be removed except for cleaning." He adds, "it would never make any pecuniary difference to me whether this condenser be used or not. All I have done is for the benefit of any amateur microscopist like myself who, wishing for a reasonably-priced condenser, can gratify that wish."—J. Webster.

—Particles too small to be discerned by a sixteenth are well seen by a twenty-fifth or fiftieth, and particles too transparent to be observed by the twenty-fifth are distinctly demonstrated by the fiftieth, and Dr. Beale suggests that the further careful study, by the aid of these high powers of the development and increase of some of the lowest organisms, and the movements which have been seen to occur in connection with certain forms of living matter will lead to most valuable results bearing upon the much-debated question of vital actions. Another very great advantage resulting from the use of the highest powers occurs in minute investigations upon delicate structures which occupy different planes, as is the case in many nervous organs. In studying the distribution of the nerves in some of the peripheral organs of vertebrate animals, very fine fibres can be followed as they lie upon different planes. The most delicate constituent nerve-fibres of the plexus in the summit of the papilla of the frog's tongue can be readily traced by the aid of this power. The finest nerve-fibres thus rendered visible are so thin, that in a drawing they would be represented by fine single lines. Near the summit of the papilla there is a very intricate interlacement of nerve-fibres, which, although scarcely brought out by the twenty-fifth, is very clearly demonstrated by this power. In this object the definition of the fibres, as they ramify in various planes one behind another, is remarkable; and the flat appearance of the specimen as seen by the twenty-fifth gives place to that of considerable depth of tissue and perspective. The finest nerve-fibres in the cornea and in certain forms of connective tissue are beautifully brought out, and their relation to the delicate processes from the connective-tissue corpuscles more satisfactorily demonstrated than with the twenty-fifth.—The Reader.

—At the meeting of the Microscopical Society, March 8th, an interesting collection of dissolving views was exhibited by the kindness of Mr. James How, of Foster-lane, by means of slides prepared by Dr. Maddox. The forms of some diatoms when thrown upon the screen measured over twelve feet in diameter; a section of echinus spine nine feet; a scale of a hawkmoth seven feet; and the blood discs of a newt from two to three feet long, every object being as sharp as a painting.