510 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



Fig. 124. 



embodies several suggestions made by his assistant, Mr. Cameron Smith. 

 It is intended chiefly for use in a physical laboratory, where minute 

 measurements of distances are very often required — such as the exact 

 amount of bending of. a rod, or of the stretching of a wire under a given 

 weight, to determine Young's modulus ; minute changes in thermo- 

 meters and barometers ; the comparison of two fiducial marks, or the 

 distance between them ; the measurement of refractive indices of plates 

 and liquids ; and numerous other purposes. 



The instrument consists essentially of a horizontal and a vertical 

 slide, along which scales to any practicable degree of fineness are en- 

 graved. The slides are actuated by 

 rack-and-pinion movement where 

 the scales are not read to a finer 

 degree than 0*05 mm.; but for 

 more minute readings a micrometer- 

 screw arrangement is adapted. The 

 Microscope proper is fixed at right 

 angles to a horizontal axis, and 

 thus turns in a vertical plane. At 

 the common focus of the eye-piece 

 ( Kamsden) and the objective a 

 finely divided glass micrometer- 

 scale is placed, giving either the 

 same reading as the verniers, or a 

 finer one. As a higher power than 

 1 in. is seldom used with this class 

 of Microscope, no fine adjustment 

 is required. A divided circle has 

 been added to the horizontal axis 

 in some instruments to enable the 

 Microscope to be placed at any re- 

 quired angle. The instrument is mounted on three levelling screws, 

 and the lower slide is set in a horizontal position by means of a circular 

 level let in at the base. By substituting a telescope object-glass for the 

 objective, the instrument is converted into a very useful "reading tele- 

 scope, by which minute measurements can be taken at a considerable 

 distance from the object. 



It will be seen from this description that readings can be taken in 

 almost every direction. 



C. Baker's R.M.S. 1'27 Gauge Microscope has diagonal rack-and- 

 pinion movements and lever fine adjustments fitted to both the body-tube 

 and the substage (fig. 125). Two draw-tubes are provided, one with 

 rack-and-pinion adjustment ; both are graduated in millimetres. The 

 length of body with draw-tubes closed is 120 mm., when extended 

 250 mm. The diameter of draw-tube is the E.M.S. No. 3 size, viz. 

 1 • 27 in., and the body 1^ in. ; when the draw-tubes and nose-piece are 

 removed, low-power objectives and photographic lenses can be placed in 

 the body, and a longer working distance obtained. The distance between 

 the nose-piece and the top plate of stage, when the body is racked back 

 to the fullest extent, is 3g in. The rotating mechanical stage has a 

 movement of 1 in. in either direction, and is graduated to 0*5 mm. The 



