and planetary features is also very largely derived from similar sources; that there is no department which is not indebted to the services of small telescopes, and that of some thousands of drawings of celestial objects, made by observers employing instruments from three to seventy-two inches in diameter, a careful inspection shows that the smaller instruments have not been outdone in this interesting field of observation, owing to their excellent defining powers and the facility with which they are used.”  Aperture for aperture, the record is more glorious for the “common telescope” than for its great rivals.  Let us for a moment recall something of what has been done with instruments which may be embraced under the designation “common” as such a statement may serve to remove impressions that small telescopes are but of little use in astronomical work.

In his unrivaled book, Webb declares that his observations were chiefly made with a telescope five and one-half feet long, carrying an object glass of a diameter of three and seven-tenths inches.  The instrument was of “fair defining quality,” and one has but to read his delightful pages in order to form an idea of the countless pleasures Webb derived from observation with it.  Speaking of it, he says that smaller ones will, of course, do less, especially with faint objects, but are often very perfect and distinct, and that even diminutive glasses, if good, will, at least, show something never seen without them.  He adds:  “I have a little hand telescope twenty-two and one-quarter inches long, when fully drawn out, with a focus of about fourteen inches, and one and one-third inches aperture; this, with an astronomical eye-piece, will show the existence of sun spots, the mountains in the moon, Jupiter’s satellites and Saturn’s ring.”  In another place, speaking of the sun, he says that an object glass of only two inches will exhibit a curdled or marbled appearance over the whole solar disk, caused by the intermixture of spaces of different brightness.  And I may add here that Dawes recommends a small aperture for sun work, including spectroscopic examinations, he himself, like Mr. Miller, our librarian, preferring to use for that purpose a four inch refractor.

As you know, the North Star is a most beautiful double.  Its companion is of the ninth order of magnitude, that is, three magnitudes smaller than the smallest star visible to the naked eye on a dark night.  There was a time when Polaris, as a double, was regarded as an excellent test for a good three inch telescope; that is any three inch instrument in which the companion could be seen was pronounced to be first-class.  But so persistently have instruments of small aperture been improved that that star is no longer an absolute test for three inch objectives of fine quality, or any first-rate objective exceeding two inches for which Dawes proposed it as a standard of excellence, he having found that if the eye and telescope be good,