134 



APPENDAGES TO THE MICROSCOPE. 



Fig. 81. 



balsam, while its upper side is bevelled off as it approaches the 

 opening, for the purpose just now specified ; and by being swung 

 between pivots in a semicircle of brass, which is itself pivoted to 

 the movable arm, it is made capable of a limited movement in 

 any direction. The upper disk, with the apparatus which supports 

 it, having been completely turned aside around the swivel-joint, the 

 object to be compressed is laid upon the lower disk; the upper 

 disk is then turned back so as to lie precisely over it, and by the 

 action of the milled-head screw is gradually approximated to the 

 lower, to which the pivot-movements of its frame allow it to take 

 up a parallel position, whatever may be the inclination of the 

 bar. — As it is frequently of great importance to be able to look at 

 either side of the object under compression, the principal plate is 

 provided with two pins at the extremity farthest from the milled- 

 head, which, being exactly equal in length to the swivel-pin, afford 

 with it a support to the instrument, when it is so turned that the 

 side represented as undermost in the figure shall be uppermost ; 

 and it is in order that high powers may be used in this case as in 

 the other, that the disk which then covers the object is made of 



thin glass, instead of 

 being (as in the original 

 form of the instrument) 

 a piece of thick glass 

 plate. Either disk may 

 be replaced with ex- 

 treme facility, if bro- 

 ken, by simply warm- 

 ing the part of the 

 instrument to which it 

 is attached, so as to 

 loosen the cement that 

 holds it. Some obser- 

 vers prefer a modifica- 

 tion of this instrument, 

 in which the brass plate 

 is made to carry an 

 ordinary Glass Slide, on 

 which the object may 

 be prepared under the 

 Dissecting Microscope 

 before being subjected 

 to compression. By 

 transferring it to the 

 Corupressorium on the 

 slide on which it has 

 been dissected, we avoid 



Ross's Improved Compressorium. 



disturbing the object, but sacrifice the advantage of being able 

 to look at it through thin glass from the under side. — The 



