1066 



RECORD OF CURRENT RESEARCHES RELATING TO 



and concentric with the object to be examined, mounted in the slide C, 

 so that whether the slide be above or below the stage, the object it 

 holds shall always be in the axis of said circular track D. This track 

 has graduation-marks placed upon it, by which the position of the 

 carriage P, that it carries, can be set and recorded. It may also be 



Fig. 130. 



Fig. 131. 



Fig. 132. 



Tised without graduations. Upon this carriage is mounted the sub- 

 stage T, carrying the holder I, to which is screwed the illumination- 

 tube I', or other accessories. 



The spindle of the holder I can turn in its socket, and be clamped 

 to it by the screw t in any position in which it may be placed, to carry 

 an achromatic illuminator or other accessory, 

 either in the radius of the track D, or at any 

 degree of obliquity thereto ; and to facilitate 

 this adjustment, it is provided with an index M, 

 resting against a graduated arc i, attached to 

 the substage. 



The apparatus is provided with a convex 

 lens L, either j)lano-spherical or piano-cylindrical 

 (the plane surface of either being modified to 

 concave or convex, if either of these forms 

 should for special purposes be deemed preferable 

 to a plane), and a plano-concave lens a, the 

 curvature of whose concave surface is the counterpart of the convex 

 surface of the lens L, the lens a being caused to traverse the surface 

 of the lens L by the movements of its carriage — in this instance an 

 arm of the carriage P, which latter also carries an illumination-tube I', 

 or a condenser arranged to direct a beam or pencil of light upon the 

 plane face of the lens a. The convex lens L is mounted upon the 

 axial end of an arm n, which arm is in the radius of the circular track 

 D, and is also carried by the substage. 



Having now fully described my invention, I claim — 



1. The combination of a circular track D in a plane parallel to 

 the optical axis XX of the instrument and coincident with the object 

 to be examined, with a substage carriage B, upon which said track is 

 mounted in a plane parallel to the optical axis, substantially as shown 

 and described. 



2. The combination of a graduated circular track D, with a 



