424 Address by the President, [Sess. 



Source of Illumination. — Diffuse daylight is the most 

 pleasant source of illumination : a northern aspect with an 

 open horizon is the best, and when this is available the 

 operator should seat himself so that the window will be upon 

 his left side. On no account must the direct rays of the sun 

 be used for ordinary microscopical work. In a town, and in 

 ordinary circumstances, it is very seldom that daylight can be 

 employed, and hence it is needful for the microscopist to get a 

 good artificial light. Among our present illuminants he has a 

 choice, but he need seek for nothing better than a good paraffin 

 lamp, with a flat wick half-an-inch broad : if he uses more 

 powerful illuminants, he must modify the light in some way. 

 The lamp should have a good steady foot, and be provided 

 with means by which the flame can be fixed at different 

 heights from the table on which it stands. Many good micro- 

 scope lamps are on the market. Fig. 1, Plate XLVIII., is 

 the illustration of a good cheap one, made by Messrs Swift 

 & Son, opticians, London. The lamp moves upon an upright 

 stem, and can be clamped at any height : it is provided with 

 a porcelain shade and a metal peak, which shade the eyes 

 from the glare of the flame. 



In Fig. 2, Plate XLVIII,, is shown the type of a more 

 developed form of a microscope lamp : it is called the " com- 

 plete " lamp, and is made by Messrs R & J. Beck, Limited, 

 opticians, London. The following is a condensed description 

 of it, as given in their catalogue. The base. A, consists of 

 a heavy ring, into which a square brass rod, b, is screwed. 

 The square rod carries a socket, c, with an arm, D, to which 

 the lamp is attached. This socket fits the square rod loosely, 

 but is kept in any position by a lever, E. On each side of the 

 burner, and attached to the arm, D, is an upright rod, G, to 

 one of which the chimney is fixed independent of the reservoir 

 of the lamp, but fitting closely over the burner, thus enabling 

 the observer to revolve the burner and reservoir and obtain 

 either a thin intense light or a broad and diffused one, with- 

 out altering the position of the chimney. The chimney, F, is 

 made of thin brass, with two openings opposite to each other 

 into which slide 3x1 glass slips. A semicircle swings from 

 the two uprights, G, to which it is attached by the pins, H, 

 placed level with the middle of the flame : to this semicircle is 

 fixed a dovetailed bar, L, carrying a sliding fitting, 0, which 



