334 FERGUSON'S LECTURES. 



l.ECT. fig. 1.) and understands how to use it, must be sensible 



vrri R TY 



the machine here referred to, is of a very different, and 



much more advantageous construction. And whoever 

 has seen the curious glass sphere invented by Dr. LONG, 

 or the figure of it in his Astronomy, must know that the 

 furniture of the terrestial globe in this machine, the 

 form of the pedestal, and the manner of turning either 

 the earthly globe, or the circles which surround it, are 

 all copied from the Doctor's glass sphere ; and that the 

 only difference is, a parcel of rings instead of a glass 

 celestial globe ; and all the additions are a moon within 

 the sphere, and a semicircle upon the pedestal. 



^e ex terior parts of this machine are a series of 

 si here, brass rings, which represent the principal circles of the 

 heaven, viz. 1. The equinoctial A A, which is divided 

 into 360 degrees (beginning at its intersection with the 

 ecliptic in Aries) for shewing the sun's right ascension 

 in degrees ; and also in 24 hours, for shewing his right 

 ascension in time. 2. The ecliptic B B, which is 

 divided into 12 signs, and each sign into 30 degrees, 

 and also into the months and days of the year ; in such 

 a manner, that the degree or point of the ecliptic in 

 which the sun is, on any given day, stands over that day 

 in the circle of months. 3. The tropic of Cancer C C, 

 touching the ecliptic at the beginning of Cancer in e, 

 and the tropic of Capricorn D D, touching the ecliptic 

 at the beginning of Capricorn in f ; each 23! degrees 

 from the equinoctial circle. 4. The arctic circle E, and 

 the antarctic circle F, each 23s degrees from its respec- 

 tive pole at N and <S. 5. The equinoctial colure G G, 

 passing through the north and south poles of the hea- 

 ven at N and S, and through the equinoctial points 

 Aries, and Libra, in the ecliptic. 6. The solstitial 

 colure II H, passing through the poles of the heaven, 

 and through the solstitial points Cancer and Capricorn, 

 in the ecliptic. Each quarter of the former of these 

 colures is divided into 90 degrees, from the equinoctial 



