338 MB. A. E. TUTTON ON A COMPENSATED INTERFERENCE DILATOMBTER. 



between the two arms of which the scale is indirectly suspended. The upper end of 

 the scale slides tightly in a short jacket which m directly suspended from the arms of 

 the bracket by two screw-pins. The jacket is pierced in front by a square aperture, 

 through which passes a projecting piece, slightly less in size, screwed firmly to the scale ; 

 above and below the aperture the jacket carries two adjusting screws between which the 

 projecting piece is firmly gripped, and which afford the desired means of adjustment. 



Fig. 6. 



A sliding piece, fixed to the scale half way down, but sliding round the rod, maintains 

 the scale strictly parallel to the rod. The mode of counterpoising the latter so that 

 the agate point may not exert undue pressure upon the object, is the same as in the 

 Zeiss instrument. The scale is divided directly to fifths of millimetres, each division 

 being consequently 0'2 millim. The drum of the micrometer is divided into 100 

 parts, the tens being figured as units. For one complete revolution the pair of hori- 

 zontal spider-lines travel vertically through half a scale division, that is, O'l millim 



