370 BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE. 



by a, tooth-and-pinion arrangement, moved by turning a 

 milled-head at the side of the main tube. Two brass 

 cells, with screws fitting the ends of the celestial eye- 

 pieces, .containing dark glasses for solar observations, are 

 sent with the instrument. 



The stand on which the telescope with its equatorial 

 parts are mounted, is of mahogany, well polished, and is 

 formed of three stout legs, about four and a half feet high, 

 cut out at the upper portions to form two branches, which 

 are jointed to the circular top, and also to the triangular 

 arms from the centre-piece, and secured firmly together 

 by brass bolts with winged-screw nuts that can be tight- 

 ened as required. At the bottom of each leg there is a 

 brass socket, with a large milled screw by the adjust- 

 ment of these screws the instrument is levelled. On the 

 centre-piece which braces the three legs firm, there is an 

 accurate compass, 4 inches in diameter, divided into 360 

 degrees, and numbered from north and south points to 90 

 degrees each way, having the usual points of the com- 

 pass engraved on its face ; the compass is fastened by a 

 bolt passing through the wood, with screw beneath, and 

 can be removed, if occasion requires it, for other uses. 



Price $300.00. 

 Additional eye-pieces, each $5.00. 



Equatorial Telescope. (Fig. 792.) This instrument 

 differs from the previously-described one in having the 

 telescope at the side of the equatorial plates, supported 

 at one end by a long axis fixed across the equatorial 

 plates, and at the other end of the axis an entire circle in 

 place of the semicircle of declination ; by this arrange- 

 ment the telescope can be revolved freely and observa- 

 tions made in the highest altitudes, which the construction 

 of the previously-described instrument does not admit of. 

 The axis is fixed across the centre of the equatorial 

 plates, and supported by two standards ; to one of these 

 standards is screwed a frame, one end carrying the ver- 

 nier, and the other the clamp and screw for tightening 

 the circle, and the tangent-screw for slow motion ; at this 

 end of the axle there is a counterpoise-weight for balan- 

 cing the telescope. The divisions on the vertical circle 

 are degrees and half degrees, numbered each way from 

 to 180, and the vernier subdividing the divisions on the 



