Page:The story of the comets.djvu/285

XV. It not unfrequently happens that a comet is only discovered after its perihelion passage, when it will be receding from the the Sun, and perhaps also from the Earth. As under such circumstances its brightness will be day by day diminishing, its visibility may only extend to a few days, or a few weeks.

From an examination of a complete catalogue of calculated

Fig. 106. ECLIPSE OF THE SUN OF MAY 17, 1882, SHOWING AN UNKNOWN COMET. (Ranyard.) comets we may obtain certain results which will here be analysed.

It appears that 492 comet apparitions have been subjected to mathematical investigation, viz.:—