MICROSCOPES. 241 



frame of mahogany eight inches square, which is covered 

 by a stout brass plate, sunk in between which there is a 

 brass plate, or wheel, cut with teeth on its circumference, 

 and movable by a pinion having a large milled-head outside 

 the plate, by which it may be turned nearly round ; to this 

 plate there are fixed short arms projecting through a circular 

 opening in the mahogany frame which extends nearly round, 

 and supporting a brass frame five inches wide and eleven or 

 twelve inches long, containing a mirror having a toothed 

 wheel attached, against which works an endless screw pro- 

 jecting through the mahogany frame and brass plates, and 

 terminating in a milled-head, by which it may be elevated 

 or depressed. Thus by turning those two milled-heads, the 

 mirror may be turned in any direction required for reflect- 

 ing the solar rays through the condensing lens, and illu- 

 minating the object. The microscopic part consists of three 

 tubes fitting easily the one over the other ; the inner one 

 containing a lens for further condensing the rays received 

 from the large lens ; on the outer end of this and the middle 

 tube, there are brass plates with openings of about half an 

 inch in the centre, and are kept together by a stout spiral 

 spring within the inner tube, between which plates the 

 slider containing objects is held, portions of the outer and 

 middle tube being cut out to allow of their introduction. 

 To the end of the outer tube, the cells containing the mag- 

 nifying lenses are screwed ; three of which accompany the 

 instrument, having different powers. To the outer tube 

 there is a small rackwork of tooth and pinion by which the 

 magnify ers may be moved gradually to or from the object, 

 adjusting them exactly to their focus of different lengths. 

 A set of objects accompany the instrument. The body of 

 the instrument and microscope tube unscrew, and the whole 

 is packed in a neat mahogany case with lock. 

 Price, with 3 inch condensing lens, and 1 rack 



motions, arranged as above described, $50.00. 

 " with 3 inch " " and 1 " " $42.00. 

 " " 5 " " " " 3 " " $75.00. 



o o 



the frame wholly of brass, $40.00. 



" 2 " " " 1 " " $35.00. 

 " "3 " " mounted in a simpler 



manner, $25.00. 



VOL. n. 21 



