ZOOLOGY AND BOTANY, iMICROSCUPY, ETC. 



421 



bench ; c, condenser with water-cell ; i in, drawing surface where the 

 image is projected ; / h, lamp-house. The lamp-house was present only 

 during a part of the exposure of the negative, hence it appears trans- 

 parent, showing the hand-feed arc lamp within : m, the large mirror 

 attached to the drawing table ; r, rheostat. The rheostat is of the ordi- 

 nary form ; s, the double pole ; there is a table switch for opening and 

 closing the circuit ; iv I, 2, supply wire to the switch and from the switch 

 directly to the arc lamp ; ?c 3, 4, 5 (upper carbon) the supply wire to the 

 switch, and from the switch to the one binding post of the rheostat (4) ; 

 from the other binding post of the rheostat (5) a wire passes directly 

 to the arc lamp (lower carbon). No current can go through the lamp 

 without going through the rheostat with this arrangement ; and with 

 the double pole switch the current is cut completely off the entire appa- 

 ratus when the switch is open. The adjustable drawing shelf has an 

 arrangement for moving up and down on metal ways which can be attached 



Fig. 58. 



to any table, whatever the form of the legs. The supporting brackets 

 are jointed, so that the shelf can be let down when the large drawing 

 table needs to be brought up close to the projection table. Fig. 59 shows 

 the Bausch and Lomb's simple drawing apparatus for the Microscope. 

 It has a hand-feed right-angled arc lamp for small carbons ; wiring and 

 connexions for the house circuit, and a rheostat which will not permit 

 over 6 amperes of current to flow. The lamp-condenser is in a tele- 

 scoping tube, so that either a parallel or a converging beam of light can 

 be obtained. The Microscope is on a support giving a drawing distance 

 of 25 cm. (10 inches), and the drawing surface is enclosed by a metal 

 shield to keep out stray light. The lamp and the Microscope are put in 

 one line. For this the lamp is adjustable on a vertical support, and it 

 can be inclined at any angle. If one finds it easier to use the mirror 

 and have the lamp at right angles to the Microscope, this outfit lends 

 itself perfectly to that arrangement. 



Fig. 59 shows the Spencer Lens Company's apparatus for drawing 

 with the Microscope. It consists of a small arc lamp with the proper 



Aug. Wth, 1913 



2 F 



