250 



slight change of the thumb determines whether one alone shall 

 move, and the object be carried up and down, or both, and the 

 object move from side to side. Figure 3 shows the principle of 

 arrangement, and figure 4 the object-holder with its springs, which 

 is held against the horseshoe by a piece of brass plate screwed 

 upon the latter, as shown in figure 1 — the object-holder sliding 

 between the two. The tray that holds the lamp is of sheet-iron, 

 5 inches by 3, with a ledge of half an inch in width at its remote 

 edge. On this tray rests a thin piece of wood of the same size, 

 covered with velvet. The lamp having its base covered with 

 velvet also, cannot slide ofi', even when the microscope is much 

 inclined, — but the lamp, with the piece of wood on which it rests, 

 is easily slid from side to side. 



Fig. 5 represents the diaphragm with the achromatic condenser. 

 This is arranged in place by sliding its foot under a spring upon 

 the same piece of wood to which the tray for the lamp is fas- 

 tened. 



The dimensions of various parts not yet given are as follows : 

 Inside dimensions of the box, length 8 inches ; width 5 ; height 

 2 ; from bottom of inside of box to binding screw, 1 1 inches. Dis- 

 tance between uprights 1|^ inch. Bearing semicircle same thick- 

 ness. Radius of this semicircle Z^ inches. Object-holder 7 -[-2. 

 Diaphragm 3 inches in diameter. 



If desired to use the microscope in the vertical position, the 

 tube must be held firmly against the supports, the tray removed, 

 and the mirror represented in figure 1 brought into its place. A 

 loose ring of plate brass capable of being made fast to the bear- 

 ing semicircle serves to fix the tube. The mirror is a plane one, 

 set in an open frame. If a plano-convex lens is placed over it, 

 it acts like a. concave mirror ; if the mirror is removed the same 

 lens may be used as a condenser. 



In packing this instrument, the tray and diaphragm go at the 

 bottom of the box, the bearing semicircle is held by the binding- 

 screw between the uprights, and the pasteboard disk is held at 

 the side of one of the uprights. The lamp and other accessions 

 go into the box. 



The leading peculiarities and novelties of the instrument will 

 now be indicated. 



1. Union of stability and portability. The base gives a suflS.- 



