ZOOLOGY AND BOTANY^ MICROSCOPY, ETC, 629 



perfect illumination of both opaque and transparent objects can be 

 obtained. 



The base A (fig. 107) 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, which is 

 pressed firmly against the square rod by a strong spring. If the 

 lever and the opposite side of the socket are taken between the 

 thumb and finger, the pressure of the lever on the bar is removed, 

 and the lamp can be raised or lowered to the desired position, when 

 by releasing the hold the lamp is at once clamped. 



On each side of the burner, and attached to the arm D, is an up- 

 right rod Gr, 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, without alter- 

 ing 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 of either white, blue, or opal glass, the latter serving 

 as a reflector. 



The reservoir, although holding enough oil to burn for several 

 hours, is made very flat, and drops into the annular base, thereby 

 bringing the flame of the lamp within 3 inches of the table, render- 

 ing it much more serviceable for direct illumination (without the 

 mirror) and for other purposes. 



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 bears a Herschel condenser P. 



This condenser, swinging with the middle of the flame as a centre, 

 is always at the same distance from it ; and thus, when once focused, 

 needs no further alteration for any change in the inclination of the 

 beam of light. The condenser is fixed at any inclination by a milled 

 head working in a slotted piece of brass K, fixed to the arm D. 



When used for transparent illumination, the condenser is not 

 required below the horizontal position ; but when the lamp is re- 

 quired for the illumination of opaque objects, the chimney having 

 been temporarily removed and the milled head fixing the condenser 

 arm having been loosened, the arm with the condenser can bo thrown 

 over the lamp, as shown in the illustration at M, and the chimney 

 being replaced, the light, which now comes through the opposite 

 opening of the chimney, can be condensed at a large angle below the 

 horizontal. 



James' 'Aids to Practical Physiology.'* — It is beyond our com- 

 prehension how this extraordinary book could ever have been written 

 by an author entitled to add M.R.C.S. to his name, or published as a 

 volume of ' Students' Aids Series ' by such publishers as those whose 



* J. Brindlcy Jamcfi, M.R.C.S., ' AMs to Practical Phybiology,' Svo, London 

 (Baillicrc, Tindall, k Cox), 1884, viii. iind GO pp. 



