Piper, a Reversible Compressoriuni with Revolving Disk. 115 



For the purpose of placing the object in position, the 

 upper disk is made to turn aside by a lateral movement, 

 after Avhich it is again brought above, and pressure applied 

 by a milled-head and fine screw, which depresses the top 

 frame to the point of contact, or as near as may be desirable. 



This movable frame is carried on a cylinder, within which 

 is a closely-fitting spring box containing the screw, sur- 

 rounded by a spiral steel coil, which separates the glasses 

 when it is required to withdraw the specimen. 



These tubes working together like the parts of a telescope 

 secure a perfectly parallel motion, while the opposing screw 

 and spring produce a remarkably even pressure. 



The box carrying the frames is mounted on an arm which 

 freely turns, for the purpose of reversing the object. At the 



opposite end of the box is placed the revolving disk, formed 

 by enclosing within a metal ring an inner tube filled with 

 cork, the edges of the tube being turned over, that of the 

 outer ring in the form of a flange, which being milled is 

 easily turned in any direction. The arm is supported upon 

 a metal pillar, made to rotate on a stout brass frame or stage- 

 plate, three inches by two, which is cut away in the middle 

 to admit the under-stage illuminating apparatus. 



This compressoriuni may be procured of Mr. Swift, 15, 

 Kingsland Koad, to Avhom 1 have given the right of manu- 

 facture. 



