H. Skey. — An Astronomical Telescope on a New Construction. 



eye-piece through an aperture left in the plane reflector. This is perforated to 

 allow of a small telescope or finder to be used, or the finder can be placed at 

 the side of the mirror as in Fig. 4. Let both plane mirror and finder have 

 a vertical motion on a horizontal axis common to both, then since " the angle 

 between the first and last direction of a ray of light sufiering two reflections in 

 the same plane, is twice the angle of the reflecting surfaces to each other," 

 and because the first direction of the ray is the same as the finder, and the 

 last direction is towards the zenith, it follows that the angular motion of the 

 finder must be twice that of the plane reflector ; this is easily accomplished, 

 and in such a manner that by merely turning the finder on to an object the 

 reflector shall move through its proper angle. 



Let AA (Fig. 4) represent a plat- 

 form fixed above the speculum, H is a 

 rod working an endless screw which 

 turns a horizontal racked wheel, B, 

 rotating on rollers running in grooves 

 between the platform and the wheel. 

 This wheel carries the pillars II, con- 

 sequently the mirror, C, and the finder, 

 D, move in azimuth with equal veloc- 

 ities. The mirror is firmly braced on 

 to the tube, TT, which carries with 

 it the wheel, E, and E turns another 

 broad wheel, F, which turns with the 

 same speed as E, for that part of it 

 which receives motion from E is equal 

 to E. The other part of F has such a 

 diameter as will give a motion to the 

 wheel, G, of double the velocity of E. 

 Fig, 4. The ratios of the diameters of these 



wheels are E = 6, small part of F = 6, large part of F = 8, and small wheel 

 G = 4. The dotted line represents a strong rod or axis, which also goes 

 through the tube T. To this axis the wheel, G, and the finder, D, are firmly 

 keyed. The finder is attached to, and moved in altitude by another racked 

 wheel, also turned by an endless screw, K ; then, whatever angular motion in 

 altitude is imparted to the finder, the mirror shall receive one-half thereof. 

 The eye piece is fixed near E, and is supported by connection with the pillars 

 so as to be independent of any vertical motion of the mirror. 



Such an arrangement gives the same degree of illumination as is given by 

 the ]S'ewtonian telescope, there are two reflections, with this difference, that 

 the light from the object is first received on the plane mirror instead of on 



