126 HISTORY OF ASTRONOMY. 



however, that the comet almost grazed the sun ; perhaps 

 some portion of its nebulosity may have come into direct 

 collision with it. The best orbits give a perihelion dis- 

 tance of -0056, or a distance of 90,000 miles from the 

 sun's surface, which is equal to about one fifth of the sun's 

 radius. 



The velocity with which the comet whirled round the 

 sun at the instant of perihelion was prodigious. This 

 was such as, if continued, would have carried it round 

 the sun in two hours and a half; in fact, it did go more 

 than half round the sun in this time. In one day (that 

 is from twelve hours before, to twelve hours after peri- 

 helion passage), it made 291 degrees of anomaly; in 

 other words, it made more than three quarters of its 

 circuit round the sun. In 40 days, the period of its 

 visibility, it had described 173 degrees from perihelion ; 

 while to describe the next seven degrees requires a 

 period of many years, and perhaps centuries. 



The head of this comet was exceedingly small in com- 

 parison with its tail. "When first discovered, many were 

 unwilling to believe it a comet, because it had no head. 

 The head was probably nowhere seen by the naked eye 

 after the first days of March. At the close of March the 

 head was so faint as to render observations somewhat 

 difficult even with a good telescope, while the tail might 

 still be followed by the naked eye about thirty degrees. 

 Bessel remarked that " this comet seemed to have ex- 

 hausted its head in the manufacture of its tail." It is 

 not, however, to be hence inferred, that the tail was 



