MO 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



support, and carrying lenses of diflferent powers, while the third has 

 a bull's-eye condenser, to which can be fixed a funnel-shaped piece of 

 blackened paper, to act as a screen. The box in which the apparatus 

 packs serves, when opened flat, as a base. 



Fig. 212. 



The speciality of the apparatus appears to consist in the numerous 

 articulations of the arms (which allow the lenses to be readily placed 

 in any desired position), and its portability — 35 cm. square by 7 cm. 

 deep. 



Zeiss's Camera Lueida. — The following is a translation of the 

 revised directions for using this instrument (see ante, p. 818) : — 



The apparatus having been attached to the Microscope by the 

 " sprung " ring, turn back the prism round the vertical pin so as to 

 allow the eye-piece to be inserted and the preparation adjusted. 

 Afterwards the prism must be brought into the position indicated in 

 Figs. 213 and 214 by the revolving motions round the vertical and 

 horizontal pins, also by the horizontal and vertical sliding movements 

 of the same pins, or where requisite by the ring as well. 



As is shown by the figures, the circular opening a in the upper plate 

 A A of the camera should be concentric with the eye-lens of the eye- 

 piece. The small bright circle, which is seen above the eye-piece 

 when the eye looks down upon it from some height in the direction 

 of the axis of the Microscope, must then appear, approximately, half 

 covered by the glass prism visible through the opening a. Seen from 



