1892.] 



MICKOSCOPICAL JOURNAL. 



67 



Durkee's Electric Illuminator. — The illuminators heretofore 

 presented in this periodical have all made use of oil as a 

 means of producing light. A neat and not very expen- 

 sive illuminator is now presented which depends on 

 electricity for the light. 



This illuminator may be attached to the mirror-bar of 

 any microscope having a swinging bar, and be employed 

 for central or oblique illumination. The construction is 

 such that when the lamp is burned out it can be replaced 

 at small expense. It is provided with a pin-hole dia- 

 phragm, cutting off all rays except those passing through 

 the object, a condensing lens, and a disc of blue glass. 



The lamp used is a 4-volt one and may be lighted from 

 a two cell storage battery or from 4 to S LeClanche cells. 

 For use with high powers it gives a very strong and 

 steady white light, assisting materially in the resolution 

 of difficult test diatoms, and bringing out the finer details 

 .of histological work. 



The cut represents two-thirds its actual size. It is 

 'made by the Mcintosh Battery Co., Chicago. 

 Photomicrographs of Diatoms. — Messrs. Trann and Witt, in 

 their work on the fossil diatoms of Hayti, describe their method of 

 photography. They first photograph the diatoms with a magnification 

 of about 100 diameters, and afterwards enlarge the negatives so as to 

 obtain a photograph magnified 500 diametei^, proper for photo printing. 

 Fine details are said to be brought out which are invisible to the naked 

 e3'e in the smaller photograph. — The Microscope. 



Photomicrography. — In an address upon photography, Prof. R. 

 Meldola, F. R. S., said there is no reason why the dry plate, which 

 has already largely superseded the eye in astronomy, should not also 

 relieve the eye of the microscopist. Many biological works have been 

 illustrated with great success by means of photomicrography, and even 

 in purely systematic works photographic illustration has been adopted 

 with success. In studying microscopic forms of life where an eva- 

 nescent plate of life-history may be full of profound significance, the 

 photographic plate might well replace the eye in those cases where pro- 

 longed and fotiguing observation has hitherto been found necessary. 



MICROSCOPICAL MANIPULATON. 



Cutting Glass Tubes, Bottles, etc. — Wrap two bands of thick 

 blotting-paper around the vessel, leaving less than ^-inch between them 

 at the place to be cut. The paper is applied while wet and is cut \ to 

 ^-inch wide. If the article to be cut is large, leave more than ;J-inch 

 between the wet bands. Apply a fine flame from 3 to 3 inches long to 

 the glass between the wet bands, slowly revolving the bottle or tube and 

 keeping the flame steadily on the glass. The clean cut along this line 

 is rapid and very satisfactory. Prof. Wm. Thompson devised the 

 process. 



Cement for joining parts of apparatus so that they will be permanent, 

 solid, and waterproof, resisting heat, oil, and acid, is made by mixing 



