Note 3 — LETTERS AND EXTRACTS FROM THE FOLLOWING GENTLEMEN.

Note.—Mr. Perry does not mean that δ Cygni is one of the most difficult tests as regards the distance of the components. He has often seen it with his 6-1/2″ Silvered Glass Reflector, and even with a stop of 5-1/2″ on the same instrument; but he was surprised at the beauty and perfection of the images—perfect and unbroken rings—and he knew that these appearances could not have presented themselves had not the figure of the mirror been of extraordinary perfection.