IJ72 BKNJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



circle into single minutes. With these differences the 

 instrument is the same as the previously-described one. 



Price $350.00. 



Fig. 793. 



\B.PIKE.JX! 



2&4 BROAD WAY. 



\NEW-YORKl 



WTicatstone's Stcrescope. (Fig. 793.) The sterescope 

 is an instrument by which two perspective diagrams, 

 being right and left eye-views of the same solid, are seen 

 at one view as solid as the object itself, or small drawings 

 having a little difference in their perspective, are made 

 to represent the complete effect of reality. This instru- 

 ment is considered as one of the most curious and beauti- 

 ful in the entire range of experimental optics. 



The body of the instrument is usually of mahogany or 

 rosewood, but the commoner ones are of tin, ja panned. 

 At the bottom there is an aperture for sliding in the views, 

 and at the front a door for admitting and regulating the 

 quantity of light. The eye-tubes are of brass, about the 

 form of those used in double opera-glasses, having pris- 

 matic convex lenses so arranged that they refract or 

 throw the images out of the direct line to the centre be- 

 tween the eyes, and each image being in this way re- 

 moved in a direction toward each other, so as to combine 



