5 28 



SCIENTIFIC RECREATIONS. 



January in that year (1801). He was quite sure of this change next day 

 (the 3rd of January), and he expressed his opinion to Bode and Oriani. 

 But letters took a long time to pass in those days, and when the other 

 astronomers had received the advices the new star had been lost in the sun's 

 glory. But after a year, on the 3ist December, 1801, the planet was again 

 seen and the discovery was proved. The new planet was named CERES. 



The discovery of Ceres led to other discoveries. For, while searching 

 for her, Olbers found other minor planets, and so on to the present day. 

 Now we have nearly two hundred asteroids, and more are probably to be 

 found in the zone beyond Mars. 



It would answer no purpose to give a list of the asteroids. We need 

 only remark that the first four were discovered in quick succession, and then 

 a lapse of thirty- eight years occurred before the fifth was found, thus 



CERES, discovered by Piazzi at Palermo, January ist, 1801. 

 PALLAS, Olbers at Bremen, March 28th, 1802. 



JUNO, Harding at Lillienthal, September 2nd, 1804. 



VESTA, Olbers at Bremen, March 2oth, 1807. 



Hencke at Driessen, December 8th, 1845. 



year. 



Since 1 848 there have been numerous minor planets discovered every 



The hypothesis that all these asteroids are fragments of one large planet 

 which has been destroyed was started by 

 Olbers ; and in confirmation of this view it has 

 been determined that the asteroids have essenti- 

 ally the same character. The orbits of these 

 minor planets are different from the larger 

 " wanderers," and cross each other, as will be 

 seen from the accompanying diagram, so that 

 a collision may one day ensue. 



Planetoids and extra zodiacal planets are 

 titles which have been bestowed upon these 

 bodies, of which VESTA is the first in order in 

 the system, and revolves in 1,325 days, at a 

 mean distance of 225,000,000 of miles from the 

 sun. JUNO and CERES take each about four of our years to revolve in their 

 orbits, at greater distances still, averaging 260,000,000 of miles. Pallas and 

 Ceres are most alike in their periods and distance from the sun ; the prin- 

 cipal asteroids are only about 300 miles in diameter, while the smaller are 

 very tiny indeed, and one certainly has quite disappeared. 



Fig- 585. Orbit of asteroids. 



JUPITER, THE GIANT. 



Jupiter has been well named the Giant planet, since his diameter is 

 eleven times greater, and he is thirteen hundred times larger than our 



