Page:The story of the comets.djvu/174

130 Previously to this, in August, the tail, according to Bouvard, was divided into two branches which were nearly at a right angle to each other. Sir W. Herschel paid particular attention to this comet, and his observations are of great value. He states that it had a well-defined planetary disc by way of nucleus, which was involved in the nebulosity forming the head. From this measurement he calculated that the diameter

THE GREAT COMET OF 1811.

of the nucleus was 428 miles. When examined with high powers the stellar character of the nucleus disappeared, and the light was spread, though not uniformly. The nucleus had a ruddy hue, but the surrounding nebulosity was of a bluish-green tinge. The real length of the tail about the middle of Oct. was upwards of 100,000,000 miles, and its breadth about