BECK'S POPULAR STAND. 93 



movement, coarse and fine adjustments to body, plane 

 and concave mirrors, revolving diaphragm, Lister's 

 dark-wells, and two eye-pieces, for 8. 



An increasing demand for good, useful, and moder- 

 ately priced instruments for students and general use, 

 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, 

 and to whom the microscope owes very many improve- 

 ments, I may mention the firm of R. and J. Beck. 

 Their Popular Microscope, fig. 49, is a fair example of 

 their excellent workmanship. 



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 hori- 

 zontal 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 novel, and possesses the fol- 

 lowing advantages ; it is strong, firm, and yet light ; 

 the instrument cannot alter from any particular incli- 

 nation it is put into, which is not unfrequently the case 

 when the ordinary joint works loose; and in every 

 position the heavier part of the stand is brought over 

 the centre of the base, to ensure an equality of balance. 



To adjust the focus of the object-glass, turn the 

 milled-heads for a quick movement, or the milled- 

 head p for a slow one. 



