216 W. K. BKIDGMAN OX A NEW 



reflector, and needing little or no interference with either the lens or 

 the lamp, while the latter may be placed at its ordinary level, and in 

 front of the instrument, and thus be altogether out of the way of 

 the hands and face. 



In reducing these views to a practical form, the following arrange- 

 ment has been found to answer the purpose very efficiently. In my 

 own instrument, to which it has been adapted, the stage is rectangular, 

 and the frame (F), figs. 4 and 5, slides in beneath it. To the under 

 side of this frame the brass plate (C) is firmly screwed at right 

 angles and parallel with its length, and upon this, which is an inch 

 and a half square and a quarter of an inch thick, the reflector- 

 carrier (Fig. 6) is held by the bar and spring (I and H), allowing 

 it to be moved about by the finger and thumb applied at the ends of 

 the tube (J), as shown in Fig. 4 ; after which, and when adjusted, 

 it may be fixed by the tightening screw (K), so as to be immovable 

 from its position. 



Now if the cone of rays be made to fall upon the centre of the 

 speculum, it will be reflected in a converging circle still ; but let it 

 be directed upon the lower edge instead, and it will then become bi- 

 sected, and only a plano-convex section will pass upwards, so that by 

 this means we shall get rid of a large proportion of the conflicting 

 rays. Then, again, if a horizontal shutter or diaphragm (D) be placed in 

 front of the speculum, as in Fig. 3, the opposite convex portion of 

 the cone will likewise be got rid of, and we shall then retain only a 

 narrow strip or ribbon of light converging in a fan -shape almost in 

 the same plane, which, for an illuminating pencil, will be a verynear 

 approach to perfection. But as some objects absorb a much larger 

 proportion of light than others, the shutter or diaphragm requires to 

 be made adjustable for distance from the speculum, in order to regu- 

 late the consequent width of the slit admitting the light, and there- 

 fore it has, as the simplest means of effecting that object, been made 

 to turn upon a pivot, as at (C), Fig. 3, and which is worked by the 

 milled head, (N), Figs. 4, 5, and 6. 



In order, also, to facilitate the adjustment of the speculum for its 

 angular position, it has been attached by a hinge at its back (Fig. 3), 

 and through the intervention of the tail-piece, (P), and the bent lever 

 acting thereon, it admits of being regulated by the screw and milled 

 head, (M), and which serves, in addition, to regulate the light during 

 observation. 



In commencing to observe a lined or dotted object requiring 



