medium. The trough should not, however, be kept filled with this solution; it should, on the contrary, be emptied immediately after use and vigorously rinsed out in clean water to protect the glass from premature deterioration.

The fluorescent or phosphorescent bodies which are to be prepared for examination should be simply placed in front of the light filter. When somewhat extensive surfaces, such as samples of rocks, chemicals, or organic objects, are to be prepared in this way for examination the surfaces should be exposed to the action of the rays at some distance from the light filter.

Luminescence Lamp No. 116.

To prepare very small fluorescent particles for observation under the microscope it will be necessary to employ a concave mirror silvered on the surface. (This mirror should be expressly ordered, if required). It attaches to the stage of the microscope, and the luminescence lamp should be so placed that its beam of light may fall on the mirror. By holding a piece of paper in front of the mirror it is easy to control the adjustment, as all papers fluoresce with a greenish light. Care should, however, be taken to prevent the rays, before falling on the mirror from reaching directly or even grazing the microscope objective or the preparation. Finally, the silvered mirror should be turned until the ultra-violet rays fall by reflection on the preparation which is to examined; but every precaution should be exercised to prevent ultra-violet light reaching the objective by reflection at the preparation, as this would

44D, engl.

17

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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 99,74 %.

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

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