A CHESHIRE CAT.—When the reflecting surface is concave the contiguous reflected rays themselves intersect, and as we pass along any line on the surface—say the line of intersection, by a given plane—the reflected rays by their ultimate intersections form a plane curve. By varying the plane of section an indefinite number of such curves result, and these all lie upon the surface known as the caustic, to which every reflected ray is a tangent. A concave lens must of necessity render originally parallel rays divergent. The principal focus of the convex lens is the point at which the rays which pass through it, near and parallel to its axis, converge. The science of optics is one that needs to be taught. BUNCH OF GRAPES.—1. We do not hold ourselves bound to inform our readers of the why and wherefore respecting our plan of conducting our paper. 2. If the terra-cotta be very dirty, sponge with turpentine, and then with soap and water. M. S. O.—No further continuation of the article on “Paper Boxes” was given in the G. O. P. “My Work Basket” is continued at intervals as space will permit. PARTICULAR.—From Angus’s “Handbook of the English Tongue,” we quote the following with reference to your query:—“In old writers, and occasionally in modern print, ‘an’ is sometimes erroneously placed before semi-vowels or vocal ‘h,’ as ‘an usurpation,’ ‘an historical account.’” Thus, you see that “a historical account” was right. You should get the book in question; it is published at 56, Paternoster-row, E.C. * * * * * [Transcriber’s note—the following changes have been made to this text. Page 394: duplicate word “sight” removed—“sight, and we”. Page 395: he to the—“of the storm.” Page 396: Dandalo to Dandolo—“Dandolo, who went”. Page 400: Weidersehn to Wiedersehn—“Auf Wiedersehn”.]