460 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



vertical tripod form of Microscope that was so popular from 1738 down ta 

 the end of the century. From the fact that no example which we have 

 seen of this instrument was furnished with a Lieberkuhn, we think it was 

 probably constructed before 1738. 



In fig. 97 the peculiarities are (1) the application of a ball-and-socket 

 inclining movement on a pillar and tripod, to Wilson's " Screw-barrel " 

 Microscope, (2) the addition of an articulated arm to carry a condensing 

 lens, for opaque objects (as in fig. 97), or a plane mirror (as in fig. 98). For 

 opaque objects the leus was removed from the body-tube and a disc having 

 a pivoted arm terminating in a ring substituted. A low-power lens in 

 a horn mount was then screwed in the ring and was thus held at some 

 distance from the instrument so that the object could be properly illumi- 

 nated. 



In fig. 98 the compound body of ivory with draw-tube is shown, also the 



Fig. 98. 



accessory apparatus. On the left are four simple lenses in disc-mounts ; 

 the ivory handle for the " Wilson," when unscrewed from the ball-and- 

 socket, having a screw-box at the end for discs of talc and rings ; the 

 forceps-carrier ; a diaphragm for the condenser (which is a bi-convex lens 

 in a cell at the lower end of the " Wilson ") ; hinged animalcule cage with 

 four concave discs of glass, mounted in apertures in a plate on which a 

 similar plate with four corresponding apertures and plane discs is hinged to 

 open or close ; condensing lens for opaque objects ; carrier with horizontal 

 rotating and vertical pivot movements for the low-power lens in horn cell, 



