ASTRONOMICAL INSTRUMENTS. 



123 



being brought to the intersection of the wires, it will then 

 be within the field of the telescope. 



In viewing astronomical objects (and particularly when 

 the greatest magnifying powers are applied) it is very 

 necessary to render the telescope as steady as possible ; for 

 that purpose there are two sets of brass sliding rods, i i, as 

 represented in the plate. These rods connect the eye-end 

 of the telescope with two of the legs of the stand, by which 

 any vibrations of the tube, that might be occasioned by the 

 motion of the air or otherwise, will be prevented, and the 

 telescope rendered sufficiently steady for using the greatest 

 powers. These sliding rods move within one another with 

 so much ease as to admit of the rack-work being used in the 

 same manner as if they were not applied. 



Improved Astronomical Telescopes. This elegant instru- 

 ment, represented below, in Fig. 132, is one of the latest 

 and most approved construction ; the stand is of polished 

 mahogany, the legs jointed and supporting the telescope 



Fig. 132. 



