File:Quarterly journal of microscopical science (1859) (14804675533).jpg

Identifier: quarterlyjournal71859lond (find matches)
Title: Quarterly journal of microscopical science
Year: 1859 (1850s)
Authors:
Subjects:
Publisher: London, J. and A. Churchill (etc.)
Contributing Library: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library
Digitizing Sponsor: Harvard University, Museum of Comparative Zoology, Ernst Mayr Library

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ition. Let a a a represent theglass sides of an aquarium, b the surface of the w^ater. Theobject to be viewed at c, with the object-glass (d). If therays from a lamp be thrown in the direction shown, by meansof the condensing-lens (e), after passing through the firstsurface they will be refracted more towards the perpendicular,and on reaching the glass wall of the tank will be reflectedback again on the object at c. It may be mentioned thatthe total reflection of the rays takes place from the outersurface of the plate glass; therefore, if a small specimen issituated in close contact with the inner surface, it may befound that there is ample space in the thickness of the plate 200 MEMORANDA. for light to pass over the object and be reflected back againto the point of adhesion with the glass. If the aquariumhas glass sides the same rule will apply, which the diagramwill illustrate, by considering the tank, condensing lens, &c.,to be in plan and placed at the side instead of the top.
Text Appearing After Image:
e. is not a lens as shown, but a short thick line representing the placeof the object. Of course, at a proper incidence, total internal reflection willalso take place from the top surface of the water alone, butI do not see how this can be made available. Object-glasses of a focus as short as half an inch may beused in the aquarium by the foUo^ving method: A tube isto be made to slide over the front of the object-glass, andextending back for two or three inches over the body of themicroscope. A very small glass prism, either right angled orequilateral, is cemented or otherwise fixed water-tight inthe end of the tube, with one of its faces nearly in contactwith the front lens. The microscope may be immersed inthe water, and used either vertically or inclined, as deep asthe ^ water-boot^^ will allow. The diagram will explain thearrangement. If the work is neatly put together, consider-able focal distance may be obtained in front of the prism,as for a half-inch object-glass it need not b

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