1893.] MICROSCOIMCAL .lolIRNAL. Ill 



ami luovinji his Tail out of tiic Light " was hi<^hly coiiiiiiciidctl 

 by Mr. Harris in his Lexicon. A novel feature of this instru- 

 ment was the series of object lenses which a])pear to have been 

 first connected with a compound microscope in this instance. 

 The numbers on the standard were to inilicate approximately the 

 position of the coarse adjustment for the diflerent poweis. To 

 counterbalance the instrument when in use, as figured, the 

 opposite end of the base had a large block of lead ilxed inside. 



The figure of Marshall's microscope has been reproduced cjuite 

 frecjuently in Encyclopa-dias and other works, and occasionally 

 the position of the candle has been criticised as being more favor- 

 able for depositing soot on the condenser than for illuminating 

 the object. The instrument, however, must be judged by com- 

 parison with the microscopes of its day and not with the perfected 

 instrument of this age. Although Mr. Harris claims that Mel- 

 len's and Leeuwenhoek's simple microscopes were the best in 

 use. he also states that for price Marshall's double microscope 

 was more satisfacforw 



Elevations along the Margin of the Lens. — Topolanski 

 ( A7. Man. f. Mug., ]March. 1S93) describes the microscopical 

 appearances in lenses which had previously been described oph- 

 thalmoscopicall}- by both JMagnus and himself. He concludes 

 that the lens is not always perfectly smooth at its margin, but 

 often shows^little undulatory, or rather tent-like, elevations. The 

 elevations are the result of the pulling action of the zonula. The 

 capsule, capsular endothelium, and lenticular fibres all take p'irt 

 in their formation. They appear first as substance or tissue ele- 

 vations, but subsequently change into an actual lifting of the parts 

 involved oH'or awav from the rest of the lens. 



Microscope Mechanical Stage. — On the under side of the 

 fixed stage is a boss with an internal thread. On the upper side 

 are guide bars with bevelled edges on which runs another stage 

 from right to left. On the right hand a bracket is fastened in 

 which is fixed l)y a gland a screw to work in the boss. The 

 gland fits into a nick in the spindle carrying the screw, so that 

 when the screw is turned it draws the plate either right or left. 

 On the top side of this plate are guide bars at right angles to 

 those on the lower plate, on which moves a third stage. On 

 the right hand and on the under side a rack is fixed which is 

 moved by a pinion. This pinion turns in the aforesaid bracket 

 and is secured by a gland, and throw's the stage from front to 

 back. .V piece in the fixed stage is cut away to allow for the 

 movement of the rack. There is sometimes a collar secured in 

 the opening of the top stage on which another stage is placed, 

 having a circular motion. 



A Slide Carriage and Object Finder. — Mr. F.J. Boettcher 

 of W asliington lias invented a carriage which is being patented 

 and which we hope to describe in our May number. 



