402 SPECIAL RESULTS IN THE UilANOLOGICAL 



lias been compared to the temperature of the focus of a 

 burning-glass of more than 32 inches diameter ( 66 ), ano- 

 ther highly meritorious astronomer ( 661 ) considers that " all 

 comets without a solid nucleus, cannot, from their exceeding 

 tenuity, receive or appropriate any solar heat whatsoever; 

 and have therefore only the temperature of space" ( 662 ) . If 

 we consider attentively the many and striking analogies in 

 the phsenomena presented, according to Melloni and Forbes, 

 by bright and by dark sources of heat, it seems, in the 

 present state and connection of our physical ideas, difficult 

 not to assume processes in the Sun itself which produce, 

 by the vibrations of an ether (by waves of different length), 

 at once radiant light and radiant heat. Mention was long 

 made in many astronomical works of a supposed occupation 

 of the Moon by a comet, in 1454, the statement of which 

 the Jesuit Pontanus, the first translator of the Byzantine 

 writer George Phranza, thought he had discovered in a 

 Munich manuscript. This supposition of the passage of a 

 comet between the Earth and the Moon, in 1454, is as 

 erroneous as is a similar assertion by Lichtenberg in respect 

 to the comet of 1770. Phranza' s Chronicles were published 

 in full for the first time, in Vienna, in 1796 ; and it is said 

 in them expressly, that in the year of the world 6962, dur- 

 ing the time that an eclipse of the Moon was taking place, 

 quite in the ordinary manner, according to the order and 

 circular path of the heavenly luminaries, a comet, similar to 

 a mist, appeared, and came near to the Moon. The date, 

 corresponding to 1450, is given incorrectly ; for Phranza 

 says positively that the lunar eclipse and the comet were 

 seen after the taking of Constantinople (19th of May, 1453); 

 and an eclipse of the Moon did really take place on the 12th 



