APPENDIX. 



An increasing demand for good, useful, and moderately 

 priced instruments fit for students and others, naturally 

 enough has had the effect of inducing makers to vie with 

 each other in their endeavours to give a better class micro- 

 scope for a small sum. Among those manufacturers who have 

 effected much for the microscope, not only in the way of 

 improvements, but in its production at a moderate cost, 

 we should have mentioned Messrs. R. and I. Beck. 

 Their Popular Microscope will be readily understood on 

 reference to fig. 357. 



The body, a (in the illustration shown as binocular), 

 is carried by a strong arm, b ; and this is attached to a 

 square bar, c, which may be moved up or down by a 

 rack-work and pinion in the lower part of the stand, where 

 the stage, d, and the mirror, e, are attached. 



The base, f, is triangular; and it is connected with the 

 parts of the instrument already described by a broad stay, 

 g, which moves on centres at the top and bottom, so as to 

 allow the end of the tube, h, to fit by its projecting pin 

 into various holes along the medial line of the base. 

 With this arrangement, if the body of the microscope be 

 required in a more or less inclined position as in the figure, 

 four holes are provided near the extremity of the base for 

 the pin of the tube to fit into. A hole near the stout pin, l, 

 is used when a vertical position is wanted ; while to obtain 

 the horizontal position, the pin of the tube is placed in a 

 hole in the stud, k, the inner surface of the stay, g, resting 

 at the same time on the top of the stout pin, l. This form of 

 construction is entirely new, and has the following advan- 

 tages : it is strong, firm, and yet light ; the instrument 

 cannot alter from any particular inclination it is put into, 



