270 SUMMAEY OF CUREENT RESEARCHES RELATING TO 



The chief novelty is the system of inclining the Microscope from 

 the vertical to the horizontal. 



The foot is a heavy triangular plate, the base 14 in. and the two 

 sides 19 in. There are two short pillars at the angles of the base which 

 support by pivots a second triangle connected at the truncated vertex 

 by a hinge with a shoulder-piece encircling the main column in which 

 the coarse adjustment slides ; the continuation of this shoulder in 

 front is the fixed stage-plate carrying the mechanical stage. The 

 lower end of the main column is provided with a female screw in 

 a pivoted sliding box-fitting, in which acts a powerful 12 in. screw 

 attached to the base-plate and controlled by a crank at the back. 

 This screw causes the main column to travel from the vertical to the 

 horizontal, the suspended triangle at the back moving correspondingly 

 as a hinged stanchion. 



The coarse adjustment is similar to that in the older Eoss model ; 

 but two racks are applied to the column and two pinions are set on the 

 same axis so that the teeth grip alternately in the racks, by which it 

 is stated that lost motion is obviated. 



The fine adjustment is also on the older Eoss principle. 



In consequence of the great length of the arm (13^ in.) carrying 

 the body-tube, and to avoid flexure and tremor, the lever is constructed 

 of two strong double bars connected by cross-bars like the beam of a 

 chemical balance. It moves between conical steel fulcrum-points 

 placed considerably in front of the centre, and very strong flat springs 

 press against each end. Upon the posterior arm of the lever a micro- 

 meter-screw of sixty threads to the inch, acts, giving a focussing range 

 of l-8th in. 



The mechanical stage rests upon the fixed rectangular plate which 

 forms one piece with the shoulder encircling the main column. The 

 mechanical movements (4 in. in all directions from the optic axis) 

 are obtained by means of two sliding plates of the usual construc- 

 tion, but with modifications in the mechanism necessitated by the 

 increase of size and greater range of motion. The lower stage-plate 

 is 12 in. from behind forward and llj in. wide, and the upper 12 in. 

 by 11 in. The ordinary rackwork motion of the upper plate was found 

 to be too coarse when high powers were employed, and an arrange- 

 ment was therefore devised by which this rackwork can be discon- 

 nected and the plate then moved by a system of four endless screws 

 on the left of the stage. 



Stage clips of somewhat peculiar form allow a slide of any size 

 from the ordinary one to upwards of 10 in. by 8 in. to be securely 

 held. At the lower end of the upper stage-plate a pair of movable 

 legs (like compasses) are applied on one axis, and can be set by a 

 screw at any angle from 10° to 160°, the end-pieces being provided 

 with grooves for the reception of the slides. An adjustable right- 

 angled arm is attached to the upper left-hand corner of the same 

 plate, and can be pressed against the slide. 



A centering substage, carrying accessory apparatus, is also applied ; 

 it is provided with rack and pinion movement actuated by the small 

 milled head on the right in fig. 40. 



