35 



On an Improved Compressorium. 

 By J. D. Hardy. 



(Communicated December 23rd, 1881.) 



My object in constructing the Compressor which I have shown in 

 the accompanying drawing is to remedy, to some extent, the defects 

 which I have found to exist in compressors as at present con- 

 structed. These defects are mainly the difficulty of regulating the 

 pressure with exactness, the imperfect parallelism, and a deficiency 

 of freedom of action, which causes great risk of losing or damag- 

 ing the object under observation. 



In the annexed figures I have shown two views of my improved 

 compressor, Fig. 1 being a perspective view, and Fig. 2 an edge 

 view. 



In these figures A is a brass plate, three inches long by an inch 

 and a half wide, or thereabouts, in the centre of which a round 

 hole is formed. At one end of the brass plate A is secured a bent 

 spring B, of thin brass, and to this bent spring is hinged a second 

 brass plate C, also formed with a round hole in its centre, and 

 bevelled on the upper surface to admit of the full action of high 

 powers. This second plate C will, when turned down, as shown in 

 Fig. 2, overlie the plate A, and the two holes will correspond with 

 each other. At the opposite end of the plate A to that to which 

 the spring B is attached, a button D is mounted so as to be capable 

 of turning freely, and also of rocking on the short stud pin d. 

 The outer extremity of this button is bored and tapped to receive 

 a small thumb screw, e. A similar thumb screw, f, is also fitted to 

 the plate C, near its hinge joint. 



A thin cover-glass is cemented to the upper side of the plate A, 

 so as to cover the central hole, and the under side of the plate C is 

 similarly provided. I have shown in the figures these cover- 

 glasses as square for the sake of clearness, but it is obvious that 

 they may be either square or round, as may be found most con- 

 venient. 



