ASTRONOMICAL INSTRUMENTS. HJJ 



hour. It is attended by four satellites, represented by four 

 balls ; they are invisible to the naked eye, but appear beau- 

 tiful through a telescope. 



Saturn, the next planet, is still higher in the system, 

 performing its circuit in about thirty years of our time ; it 

 moves at the rate of 22,298 miles an hour ; it is accompa- 

 nied by seven satellites, and a large luminous ring. 



Greorgium Sidus, or Herschel. is the seventh planet in our 

 system ; it is nearly twice the distance of Saturn from the 

 sun, round which it revolves in about 90 years ; its diame- 

 ter is 34,1 70 miles, and it is accompanied by six satellites. 



Price, $50. 



Fig. 123. 



Improved Planetarium. (Fig. 123, as above.) This in- 

 strument has received the entire approbation of teachers, 

 and others, who have used it, and has been adopted in 

 most of our academies and schools. It is substantially made, 

 the planets moving by a crank and wheel-work within the 

 box, on the top of which is an engraved plate representing 

 the signs of the zodiac, &c., and the whole as useful an 

 instrument as the more costly one preceding. 



Price, with brass stand, $15.00. 



" with mahogany stand, $ 7.50. 



The Common Orrery. (Fig. 124.) The following shows 

 one of these instruments of a simple form : It consists of a 

 table, upon the top of which are delineated the signs of the 

 zodiac, points of the compass, days of the month, and 

 months of the year. In the centre is a strong wire or brass 

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