PROCEEDINGS OF SOCIETIES. 91 



The next step in its further development arose from the observa- 

 tion, that, when the wooden block was set upright, on the angle 

 formed by the strut, or projecting ridge, and the bed, it inclined 

 nearly at the angle, or diagonal direction, in which the microscope 

 is usually employed, and that by shortening the block slightly on 

 one side of the ridge the most comfortable position for observation 

 could be readily secured ; the clamp or saddle carrying the body 

 being then attached over the upper extremity of the block. It 

 therefore merely required a stage and mirror to render the instru- 

 ment serviceable in this new form. This was effected, keeping the 

 portability of the result always in mind, by inserting into the 

 under surface of the block, at a proper distance, a dovetailed 

 socket for the reception of an elongation, or tongue, of a moveable 

 stage-plate, and below this a small ferrule was introduced for carry- 

 ing the rod of the mirror. 



It was also found that, by elongating the rod, and craning the 

 body of the instrument over into a vertical position, it miglit be 

 employed as a dissecting microscope ; the only addition that was 

 required being the insertion of another dovetailed socket into the 

 block to carry the stage-plate in a horizontal position. With these 

 various adaptations to the circumstances as they presented them- 

 selves, the little instrument assumed its perfect form. 



As tills original microscope was of inconvenient size and weight, 

 and as tliere was no apparent reason why these objections could not 

 be easily obviated, I determined to have a new one made, maintain- 

 ing the same form and construction, but reducing the weight and 

 dimensions wherever it was practicable ; the result has been the 

 small instrument which was submitted to the Members of the 

 Society on Wednesday last, and which I shall now proceed to 

 describe in detail. 



The block, or bed, is made of oak, or other heavy wood, of about 

 half an inch in thickness, and is Ti inches long by 3 inches wide. 

 Into this are countersunk the two brass dovetailed sockets, the 

 diagonal one, or that which carries the stage plate in a diagonal 

 position, and at right angles to the bed, at 3^ inches from the upper 

 edge, the horizontal one at 3 inches ; the circular socket for receiv- 

 ing the rod of the mirror being inserted about 1^ inch from the 

 lower edge. At the back of tiie block are introduced two circular 

 ferrules, 3J inches from the top, for the reception of two strong 

 pins, which connect the strut, or upright piece, with the bed ; this 

 arrangement enables us to remove this from its position, and to 

 pack the whole in a much smaller compass. In the side of the bed 

 is also inserted another ferrule to receive the pin of a condensing 

 lens for concentrating the light on the stage for opaque objects, or 

 for the same purpose between the source of light and the mirror, 

 it is placed 2^ inches from the top. 



The strut, or upright piece, is of the same width and thickness 

 as the bed, and 3^ inches in heighth, having two strong pins inserted 

 for connection with the main piece. 



The stage is a single stout plate of brass, of the same width as 



