_Telescopic Comets_ vary in size to a considerable degree. In diameter they generally range from about 1′ to 7′, and are usually round, with a bright centre like the globular clusters Messier 2, 3, 13, 15, 49, and 92, as seen with a low power; but occasionally they are faint diffused masses, like the planetary nebula near β Ursæ Majoris, M. 97, or the large nebula S. of ξ Cassiopeiæ, in the New General Catalogue, No. 185, R.A. 0^h 33^m, Dec. 47° 44′ N. In brightness they range from being visible to the naked eye to objects of the last degree of faintness. They average some 2′ or 3′ diameter, but are sometimes less than 1′; so that the power of the sweeper should be capable of readily showing an object of this size as it passes through the field. The observer should turn his instrument upon the small planetary nebula N.G.C. 1501, R.A. 3^h 57^m, Dec. 60° 37′ N. in Camelopardus. It is about 1′ diameter. He should also pick up N.G.C. 6654, R.A. 18^h 27^m, Dec. 73° 6′ N., which is a star of about 12½ mag. involved in a pretty conspicuous nebulosity. Swift describes the latter as looking just like a comet. N.G.C. 6217, R.A. 16^h 38^m, Dec. 78° 25′ N., is also a small nebulosity which might easily be overlooked with a low power. Let the observer examine the three objects named, and he will gather a good idea of a small telescopic comet, especially from N.G.C. 6654, which may be readily found, as it is in the same field as χ Draconis, and visible at any time of the year and night. N.G.C. 6643, R.A. 18^h 23^m, Dec. 74° 32′ N., is near the latter, but it is a brighter object. The observer will find two tolerably plain nebulæ in the same field at about R.A. 6^h 52^m, Dec. 85° 56′; so that they are only 4° from the pole. They are N.G.C. 2276 and 2300. These objects ought not to elude detection in any instrument properly adapted for comet-seeking.