642 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The present instrument is very well finished in brass, mounted on a 

 circular brass base, has a movable concave mirror in the drum, and a 

 bullseye condenser fixed by a dovetailed fitting for the illumination of 

 opaque objects. The coarse-adjustment is effected by sliding tube, and 

 the fine-adjustment by a screw movement to the stage. Nine achro- 

 matic objectives are provided, some doublets, and some triplets, ranging 

 in power from 65 mm. to 1*7 mm. ; also six eye-pieces (one missing), 

 giving amplifications from 9 to 1790 diameters, according to the table 

 supplied. There is also an eye-piece with needle-points for measuring 

 objects, and two stage micrometers : 1 cm., ruled in 100 parts, and 

 1 mm., also divided in 100 parts. 



Old Microscope presented by Mr. Albert Ash. — This old Micro- 

 scope (fig. 79) is an improved form of Culpeper and Scarlet's "double 

 reflecting" model, first introduced about 1750, and was called by 

 Adams, in 1798, "the common three-pillared Microscope." It is well 

 made, all in brass, with the three scroll pillars screwed on to the square 

 mahogany box containing the various apparatus ; amongst these are a 

 lieberkuhn, concave mirror, bullseye condenser, and six objectives. 

 This model enjoyed great popularity from 1750 onwards on account of 

 its cheapness and handiness, and was extensively copied by all makers of 

 this period. The focusing was effected by sliding the tube carrying the 

 eye-piece and objective up and down the fixed body-tube, but early in 

 the last century, when rack-and-pinion had been generally introduced 

 for the purpose of focusing, this model was further improved by the 

 addition of a rack fixed to the bodv-tube and working through a slot. 

 Ihis improvement could readily be fixed to the older models, and there 

 is no doubt that this specimen was so altered at some later period, for 

 the colour and lacquer of the brass used for the rack and inner tube are 

 different from that of the rest of the Microscope. 



Old Microscope presented by Mr. C. F. Rousselet. — This old 

 Microscope (fig. 80), made entirely of wood and cardboard, is a model 

 which was extensively manufactured at Nurnberg, in Germany, for 

 about a century from 1750 onward. It is a simple and cheap imita- 

 tion of Culpeper and Scarlet's " three-pillared double reflecting Micro- 

 scope." The optical part consists of three simple biconvex lenses ; 

 two of these, forming the eye-piece, are mounted in a cardboard tube 

 with wooden ends, and are held in position by a wire ring ; the third is 

 very much smaller and more convex, is provided with a pin-hole metal 

 diaphragm, and forms the object-glass of about J-in. focus. The com- 

 bination, therefore, is that of a chromatic compound Microscope, giving 

 a total magnification of about 45 diameters. The focusing is effected 

 by sliding the cardboard tube carrying the object-glass up and down the 

 fixed body-tube. A movable plane mirror fixed to the centre of the 

 foot-plate serves to illuminate transparent objects ; these were mounted 

 on a wooden slider held in position by a wooden clip and spiral wire 

 spring. 



The underside of the wooden base shows a mark burned in with 

 red-hot iron, which is understood to be a Nurnberg trademark. 



