Page:Hardwicke's Science-Gossip - Volume 1.pdf/217

not be despised by the readers of Science Gossip, however learned; and if it may chance to meet the eye of one immersed in the speculations of gain, or given up to studies he may fancy more noble and exalted, and who may be disposed to treat with indifference subjects seeming so lowly and common, let his rising contempt be cheeked by the reflection, that the humblest thing in nature becomes an exalted subject of human study, when considered as an object for which Infinite Wisdom has exercised design, and upon which the finger of Omnipotence has put forth its power.

Armagh.Lewis G. Mills, LL.B.

In making dissections of the lower animals, I have frequently found that much more satisfactory results are attained by the employment of low magnifying powers of considerable penetration, than by the use of the inch and half-inch lenses of such instruments as the Quekett microscope. The advantages of low powers are:—1st. That an abundance of room is left between the lens and the object, so as to admit of freedom of action of the operator's hands; 2ud. That the object may be easily and well illuminated by means of the "condenser;" and 3rd. That several structures situate at different levels are brought simultaneously into view. From a knowledge of the qualities I have alluded to, I was led to think that an arrangement of simple lenses for the production of binocular vision would be of infinite service to the anatomist. I therefore caused such a combination to be effected, and, having added to it a few contrivances calculated to facilitate dissection, I now submit the result to working microscopists.

The microscope when closed and packed, with its various apparatus, forms an oblong mahogany box about six inches long and three and a half inches deep, provided with a lock and key. When unlocked, the cover and one side, which are connected by hinges, unfold so as to lie out in front of the operator, displaying, at the same time, the lenses, mirror, and dissecting instruments. The stage consists of a gutta percha trough, having a small circle of glass cemented into its centre, and placed (when in use) upon ledges attached to the two ends of the case. The objects of this species of stage are:—(a) to enable mollusks and similar creatures to be dissected under water; (b) to allow the object to be fixed by means of pins which may be driven into the gutta percha; and (c) to permit light, when required, to travel through a tissue, by being reflected from the mirror to the glass circle. Outside the real ends of the case, which sustain the trough, there are two false ones, slightly bevelled above and connected below with horizontal pieces, which slide easily and uniformly into the bottom of the case. These are intended as supports for the wrists of the anatomist, and can be drawn out for a distance of six inches or less on either side. The lenses, which are two in number, are fixed in movable eye-pieces, and these are sunk in an oblique arm, which has the power of vertical rotation on the perpendicular bar employed in producing the proper focus. This vertical bar slides freely and steadily in a brass fitting which perforates the back of the case. By means of the rotating power to which I have referred, the arm bearing the lenses is, when not intended for use, depressed so as to fit into the centre of the case. The trough also slides beneath the mirror. When the object examined is opaque, a "bright spot" of light is thrown upon it by the condenser which springs from the front angle of the case. The dissecting instruments are placed in depressions in those portions of the case which unfold upon the table; they consist of two pair of scissors ("curved" and "straight"), two curved and two straight needles, and a pair of scalpels of forms adapted to the requirements of the dissector.

The magnifying power, with the binocular arrangement, does not exceed six diameters, but the field of view is so large, and the "relief" of the object under examination so well and clearly marked, that it is not without some degree of confidence that I ask the readers of Science Gossip to pronounce their opinion upon the qualities of the new binocular.

The pretty green frustules of Cosmarium botrytis may be found in almost every pond, and form very interesting objects for the microscope. Each frustule is a perfect plant; and consists of a single cell, having a deep constriction across the middle, and regularly covered with minute tubercles. The