2O HOW TO WORK 



Messrs. Smith and Beck, and since modified for paruffine, represented 

 in pi. XI, fig. 46, gives a white light, and produces very little heat. 

 Of oil lamps there are several which serve for microscopical examina- 

 tion. The German Argand lamp, lately imported into this country 

 by Mr. Pillischer, is a good microscope lamp, and so also is the 

 ordinary French moderator, especially if provided with a blue or 

 neutral tint glass chimney, and a shade. But these lamps, and indeed 

 gas itself, yield to paraffine and belmontine which give an exceed- 

 ingly steady and white light with very little heat. 



25. Paraffine Lamps. For some years past I have been in the 

 habit of using one of the common little paraffine lamps, termed night 

 lamps, with a small round wick, which may be bought for I.T. 6d. 

 pi. XI, fig. 47. This gives a very white light, and is most convenient, 

 as well as economical. A pale blue glass chimney improves the 

 quality of the light, and a shade protects the eyes from the general 

 glare. I use this lamp with the fiftieth, and find that it works ad- 

 mirably. 



Mr. Collins sells an excellent paraffine lamp under the name of 

 the " Bockett Lamp," which is provided with an adjustable silvered 

 reflector, a bull's eye condenser, and a blue glass chimney. One of 

 these has been fitted up with a round wick, like the little lamp 

 above referred to. I do not think anything more simple or con- 

 venient for microscopical purposes can be obtained, fig. 48, pi. XL 



26. Gas Lamps. For those who prefer gas I recommend the 

 gas lamp of Mr. Highley, which is provided with a flat brass plate 

 and a water bath, instruments of great use in microscopical investi- 

 gation, pi. XI, fig. 49. The light is made to pass through an open- 

 ing in a diaphragm, so that the eyes are quite protected from the 

 diffused light. A very pleasant light is produced, as in other lamps, 

 by causing the rays to be transmitted through a blue chimney glass 

 and a flat piece of neutral tint glass. The objection to this lamp is 

 its great heating power. 



The eye not observing should always be kept open, but protected 

 from the direct glare of the microscope lamp. For this purpose a 

 shade made of black paper may be fitted to the body of the instru- 

 ment at a convenient distance below the eye-piece. 



Of examining the Surface of Objects by Reflected Light. 



Ordinary diffused daylight or lamplight may be used for this 

 purpose, but this mode of illuminating opaque objects will seldom 

 give satisfactory results. Unless sunlight or some other very power- 



