34G 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



It has rack-and-pinion coarse adjustment, and the fine adjustment 

 is by micrometer-screw. The base is a folding tripod with joint for 

 inclination. It is furnished with draw-tube, double mirror, and iris 

 diaphragm. The leather or walnut case, in which it is packed, measures 

 only about G^ by 4^ by 8£ in. 



Beck's Process Microscope.*— The Microscope illustrated in fig. 55 

 is specially designed for the examination of " surfaces " in any branch 

 of photo-mechanical work. It is very useful in examining the form of 

 the dots in half-tone work and for watching the process of etching. It may 

 also be used for ascertaining the grain of a collotype or for examining 

 the three-colour work as it comes off the machine. The instrument has- 

 a rack-and-pinion movement for focussing with draw-tube. The 

 illumination is provided by a jointed condenser, which can be made to- 



Fig. 55. 



move in any direction. The Microscope, with its long arm and heavy 

 base, can be used where desired ; or it may be screwed to the bench and 

 the plates passed under it. 



Beck's Pathological Microscope.f — This is called Stand No. 17 by 

 the makers, and is shown in fig. 5(5. The build is that of the tripod 

 base and pillar model, and is as rigid and well balanced in the horizontal 

 as in the vertical position. The coarse adjustment is by rack-and-pinion. 

 The patent fine adjustment is by means of a lever actuated by double 

 thread screws, which give the two speeds of -^ in. and y^ in. for one 

 complete revolution of the milled head. The fine adjustment is so 

 placed that it can be used without raising the wrist from the table. The 

 mechanical stage has a 2-in., motion in the lateral direction and a 

 1-in. in the vertical. It is divided and engraved in ^ in. for 

 purposes of "finding." There is a spiral rack-and-pinion focussing 

 and screw centring substage and a double mirror. 



* Messrs. R. and J. Beck's Catalogue, London, p. 4S. 

 t Tom. cit., p. 38. 



