d. Codeword

No. fe s.

100. The Three-lens Condenser of N. A. 1.40 is primarily

intended for use as an immersion condenser, and when so used will render the lull aperture of an oil-immersion objective available for observation. It can be used with excellent results in the examination of objects embedded in a highly refracting medium. It can also be used in conjunction with the Centre Iris Diaphragm No. 104, or with the Centre Stop No. 105 for dark - ground illumination............................................1.0

101. The Aplanatic Condenser is an application of the principle of oil-immersion lenses and, like these, is chromatically and spherically corrected and satisfies the sine condition. Its focal length is 8.5 mm and the working distance is 1.2 mm, which admits of the use of object slides up to 1.2 mm thick. This condenser is capable of extensive and varied application. In ordinary observation it may serve as a dry condenser of N. A. 1.0, and it offers special advantages in photo-micrographicwork owing to the uniform and colour-free illumination which it supplies. When used as an Immersion Condenser of N. A. 1.40 it may be made the means of obtaining

very wide angled or very oblique illuminating pencils.

Its great light-gathering power is of considerable practical advantage in observations under high magnifications.

As an illuminator in connection with photo-micrographic work. it reduces the requisite time of exposure by about 30%*) When used in conjunction with a centre stop placed upon the diaphragm carrier it constitutes a very efficient dark-ground condenser furnishing illuminating pencils having numerical apertures ranging from 1.1 to 1.40.

As a result of its very high degree of aplanatic and chromatic correction the image as seen in the eyepiece is remarkably free from colours and the effects of diffraction and reflections.

Aplanatic Condenser of N. A. 1.40 in screw mount . 3. (

*) Dry mounted preparations, such as the usual kinds of test slides of scales and diatoms, are not adapted for testing this condenser, and they are not rendered so by the interposition of a layer of immersion-oil, since the total reflection which occurs at the upper surface of the slide prevents the effective aperture from rising above N. A. 1.0-

Aplanatic Condenser, of N. A. 1.40.

0. Illuming

. 0 Illumi

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Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,48 %.

La langue de reconnaissance de l'OCR est l'Anglais.

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