948 dV THE INDIAN, &C. 



the Other without, the first mentioned circles, and 

 representing two secondaries of the ecliptick. On the 

 two other pins a circle is placed, which encompasses the 

 Avhole instrument, and within which the different circles 

 turn : it represents the meridian. Within the inner 

 secondary of tlie ecliptick a circle is fitted to it, in the 

 same plane, and turning in it. This is adapted to 

 measure latitudes. To this internal circle, two aper- 

 tures, or sights, opposite to each other, and without its 

 plane, are adapted, like the sights of an instrument for 

 altitudes. The armillary sphere is complete when con- 

 sisting of these six circles. The ecliptick and seconda- 

 ries are to be graduated as minutely as maybe practica- 

 ble. It is best te place both secondaries, as by some 

 directed, within the ecliptick, (instead of placing one 

 of them without it,) that the complete revolution of 

 the outer secondary may not be obstructed by the pins 

 at the poles of the equator. The Meridian, likewise, 

 should be doubled, or made to consist of two circles ^ 

 the external one graduated, and the internal one moving 

 within it. Thus the prole may be adjusted at its proper 

 elevation above the horizon of any place. , The instru- 

 ment so constructed consists of seven circles. 



*' It is remarked, that when the circle, representing 

 the meridian, is placed in the plane of the true meridian, 

 $0 that it cuts the plane of the horizon at right angles, 

 and one of the poles of the equator is elevated above 

 the horizon conformably with the latitude of the place } 

 then the motions of all the circles round the poles re- 

 present the motions of the universe. 



" After rectifying the meridian, if it be wished to 

 observe the sun and moon together, the.outer secondary 

 of the ecliptick must be made to intersect the ecliptick 

 at the sun's place for that lime ; and the solstitial 

 colure must be moved until the place of intersection be 

 opposite to the sun. Both circles are thus adjusted 

 to their true places ; or if any other object^ but tt\e 



