mere discovery of these objects Herschel quickly surpassed all others. In 1786 he published a catalogue of one thousand new nebulæ, in 1789 a catalogue of a second thousand, and in 1802 one of five hundred. In all he discovered and described two thousand five hundred and eight new nebulæ and clusters. This branch of astronomy may almost be said to be proper to the Herschels, father and son. Sir John Herschel re-observed all his fathers nebulæ in the northern hemisphere, and added many new ones, and in his astronomical expedition to the Cape of Good Hope he recorded almost an equal number in the southern sky.
Of the six thousand two hundred nebulæ now known the Herschels discovered at least eight-tenths. The mere discovery of twenty-five hundred nebulæ would have been a brilliant addition to our knowledge of celestial statistics.
Herschel did more than merely point out the existence and position of these new bodies. Each observation was accompanied by a careful and minute description of the
