528 RECORD OF CURRENT RESEARCHES RELATING TO 



It consists simply of a circular piece of glass, of the form and mounted 

 in the manner shown in Figs. 47 and 48 (Fig. 47 being a section, 

 on the line A B, of Fig. 48), and placed with the plane side in front of 

 the centre of the eye-piece, as in Fig. 49. This plan enables the 

 camera to be placed closer to a deep eye-piece. The effect is, however, 

 precisely the same as in the Spencer form, but a little more trouble 

 is required to get the reflecting surface into the right position, which 

 is however compensated for by the greater economy of construction. 



Reflecting Plates for Microscopical Investigations. * — Herr 

 Hilgendorf points out that it is often difficult or impracticable with 

 flat objects to bring the sides (or with elongated objects, the ends) into 

 the proper position for observation. The author uses, in such cases, 

 a small strip of reflecting plate (silver-leaf, such as can be detached 

 from ordinary looking-glass or silvered cover-glass), which is attached 

 to a piece of glass from about ^-1 mm. in thickness. The short 

 side of the latter is ground to an angle of 45°, and the facet thus 

 obtained carries the little reflecting plate. This, turned upwards, is 

 put close to the surface to be examined, which is in a perpendicular 

 position ; by looking from above into the reflector, the reflected image 

 can be observed in a position somewhat sideways from the original, 

 and at a lower level. The nearer the object is to the reflecting plate, 

 the sharper and higher the image appears. Direct application to the 

 reflecting surface would therefore be the most advantageous ; but in 

 this case transmitted light, or at least central light, must be dispensed 

 with in the examination. Transverse sections of hairs lying hori- 

 zontally have been shown by the author by this method. The ex- 

 tent of amplification with which the reflector can be used depends 

 not only on the nature of the object, but on the perfection of the 

 reflector. With imperfectly arranged contrivances, the use of an 

 amplification of about a hundred times has been found possible. Con- 

 sidering the cheapness of the reflectors, their application is much to be 

 recommended for prej)arations whose sides would otherwise be 

 invisible. The author suggests that the same reflectors reversed, that 

 is, with the reflecting surface turned downwards, could be made avail- 

 able for illuminating laterally an object placed close beside them. 



Parkes's Microscope Lamp with Cooling Evaporator. — This 

 lamp (designed by Messrs. Parkes, of Birmingham) is shown in 

 Figs. 50 and 51. A is a lacquered brass stand, with heavy foot ; B the 

 brass lamp, capable of holding paraffin for eight hours' consumption. 

 This may be raised or lowered on the sliding upright from 4 to 12 

 inches ; that is, the burner is 4 inches from the level of the table, when 

 at its lowest point. C is a bronzed copper cylindrical shade, 3 j inches 

 diameter, with hood at front to prevent the upward reflection of light. 

 At the back is a parabolic reflector transmitting nearly parallel rays, 

 which will slide out for cleaning ; when desirable a disk of cardboard 

 may be placed over this reflector, for " white cloud " illiunination. At 

 the front is a tinted glass " light modifier," which is secured by a 

 bayonet joint, and may also be removed when necessary. 



* ' SB. Gesell. Xaturf. Freunde zn Berlin,' 187lt, p. 2. 



