716 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



The following are some of the dimensions of this toy : — Total height 

 of A 1| in. ; diameter of base 1 T V in., diameter at centre ff in. ; height 

 of dome C |f in. ; height of E between screwed parts f in. ; height of 

 D f^ in. ; diameter at top f in., at bottom §§ in. 



Watson's Junior Metallurgical Microscope.* — This instrument 

 (fig. 78) is on the lines of an ordinary Student's Microscope, but the 

 stage is a solid one designed especially for holding metal specimens, and 

 can be raised and lowered in the optic axis, and permits of a separation 

 between the nose-piece of the Microscope and the surface of the stage 

 of 5 in. 



The interest which is being shown in the study of Metallurgy has 

 caused students to inquire for an instrument of simple form and less 

 costly design than the large models which have hitherto been available. 



Zeiss' Measuring Microscopes.f — 1. Microscopes for Metal Testing. 

 Models A, B, C of these instruments are intended for the measurement 

 of short lengths of metals (to 20 mm.), with an accuracy of O'Ol mm. 

 Their upper structure is essentially alike, and consists mainly of an 

 ordinary Microscope with rack-and-pinion, the Microscope being movable 

 on a horizontal slide by means of a screw of exactly 1 mm. thread. The 

 spindle is rotated about its long axis by a micrometer drum whose 

 circumference is graduated to a hundred parts. Each part corresponds, 

 therefore, to a longitudinal movement of the Microscope equal to 

 • 01 mm. The magnification of the Microscope can be adapted to the 

 object by alteration of objective and ocular. Models A and B have 

 been constructed to the design and requirements of Dr. Schwinning. 



Model A (plate XX. fig. 1). The object is placed on a simple ebonite 

 stage-plate. The horseshoe foot rests on its base with four points only, 

 two of the points being the rounded ends of the screws S x and S 2 . If the 

 piece of work, on which the measurement is to be made, be large enough 

 and approximately plane, the Microscope can itself be placed thereon 

 and sharply adjusted with rack-and-pinion on to the object at a distance 

 •corresponding to that of the stage-plate T. The whole of the upper 

 structure of the Microscope is fastened to the lower part merely by 

 means of a stout horizontal plug fitting into a strong cut collar H 

 clamped by a screw K. It is thus possible to remove the upper part 

 and adapt it to a laboratory stand for more convenient examination of 

 any large object (plate XX. fig. 2). A magnification of 15-20 diameters 

 is found to be sufficient. 



Model B. This is especially intended for measurement in two 

 mutually perpendicular directions. This convenience might be of im- 

 portant application in certain cases (e.g. in testing surfaces not perfectly 

 plane), and is attained by equipping the lower part with a rotatory object- 

 stage bearing on its circumference two grooves at 90° apart into which 

 a spring engages. After measurements in one direction, the stage is 

 rotated through 90°, and then a second series of measurements can 

 be made. The upper part of the Microscope remains the same as in 



* Watson and Sons' Special Catalogue, 1906. 



t Carl Zeiss' Special Catalogue, Jena, October 1906. 



