Page:The story of the comets.djvu/137

this idea Kirkwood gave reasons why some connection may exist between Nos. 2 and 3 in the above table.

No. 1 was discovered by Westphal at Göttingen on June 27, 1852; and subsequently and independently by Peters at Constantinople. It was described as "pretty bright", and "above 1' in extent"—language which does not err by being too definite.

No. 2 was discovered by the indefatigable Pons on July 20, 1812, being the 16^th comet found by him in 10 years. It had an irregular nebulous form without tail or beard, and was only visible with the aid of a telescope. Encke having assigned to it a period of about 703/4 years the return of the comet was anticipated about 1883, and accordingly a sweeping ephemeris for it was computed by Schulhof and Bossert. By the aid of this, Brooks in America found it on Sept. 3. It seems to have exhibited at this visit physical characteristics differing altogether from anything recorded in 1812, unless we assume that the observers of that date failed to do justice to the comet's features. Chandler in America and Schiaparelli in Italy saw it on several occasions in Sept. 1883, first as a nebulosity, then as a star, and then as a nebulosity again; whilst Müller at Potsdam on Jan. 1, 1884, observed changes backwards and forwards in magnitude and brightness to the extent of 7/10ths of a magnitude, in 13/4 hours. Trépied observed it daily from Jan. 13 to 18 without noticing anything very remarkable; but on Jan. 19 the aspect of the nucleus had so changed that it was difficult to realise that the same object was being scrutinised as had been viewed on previous days. The head then exhibited 3 distinct zones as in Fig. 39.

"The interior and most brilliant zone was almost circular, and remarkable owing to its milky aspect: it stood out sharply from the adjoining zone and was of a leaden hue: outside this second zone came the ordinary nebulosity of the tail, having on the south-west side a parabolic outline. "The nucleus had undergone a considerable lengthening; it consisted of 2 distinct parts of very different brilliancy united by a very well marked twisted link (étranglement) which occupied almost the centre of the inner circular zone. The Southern part of the nucleus, which was by far the brightest, was terminated by an elliptic arc very sharply denned and tangential to the circumference of the zone; the Northern part on the contrary was suddenly cut off at the extremity of the diameter, whose