ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



937 



Fig. 208. 



Fig. 209. 



readily discovered in the manner above described ; but if tlie urine 

 contained a few blood-corpuscles or casts, they could not be thus dis- 

 covered. The film of liquid held between two [small-sized] glass 

 slides by capillary attraction is so extremely thin that objects sparingly 

 contained in the urine would not be discovered. If, however, a small 

 cover-glass be used, and the movable tube be placed above the slide 

 so as to clamp it from above instead of from below [this we under- 

 stand to have been carried out in the newer form], and thus avoid 

 pressing the cover-glass against the edge of the notch, a thicker film of 

 liquid is examined, and the instrument answers very well. But its 

 utility would be greatly increased if a plane mirror were fixed in a 

 removable tube at the end of the instrument, so that it could be used 

 in the upright posture as well as, if desired, in the horizontal. All 

 practitioners know how desirable it often is, in examining a urinary 

 deposit, to have a very thick film of liquid, and this is impossible 

 unless the Microscope is vertical in position." 



The difficulty we have found with this instrument is the great want 

 of light, notwithstanding the condensing lens ; and it cannot, we are 

 bound to say, be compared with the 

 small pocket Microscope designed and 

 made by Mr. Swift and described by 

 Professor G. T. Brown (Figs. 208, 209), 

 which is more compact — 3 x f inch 

 — and is far more convenient to use. 

 It is provided with a mirror G, which 

 can be removed when desired, and the 

 piece which is seen projecting on the 

 right enables full-sized slides to be 

 used. It has also an achromatic con- 

 denser with diaphragm for oblique light 

 as well as dark spots ; and according to 

 our experience, hardly leaves anything 

 to be desired where an instrument is 

 necessary which has to be in reality, and 

 not in name only, a " pocket Micro- 

 scope." (A is the main outer tube ; D 

 an inner tube carrying the objective and 

 sliding within A for the coarse adjustment ; E a third tube which 

 supplies a fine adjustment. Within B is a spring tube which holds 

 the slide C in position.) 



Sidle's "Acme" Lithological Microscope. — This (Fig. 210) is 

 on the general plan of the " Acme " models (see vol. iii. (1880) p. 522, 

 and ante, p. 657), but in lieu of the rotating stage-plate there is a 

 permanent rotating stage graduated to degrees. 



The polarizer is mounted on swinging arm to allow of being 

 turned out of the way when not in use, and is furnished with a 

 graduated circle and index, and a spring click showing when the 

 prisms are crossed. It will receive a lens-system of extreme angle 

 at its upper end, which, together with a corresponding system adapt- 

 able to the 1^-inch screw in body-tube, serve to show the rincrs 



