P.S.--I see that Johnson's _Dictionary_ gives the same statement about _enough_ and _enow_. This answer is therefore superfluous. Johnson gives numerous instances of the use of _enow_ from our best authors. H. C. R. * * * * * PHOTOGRAPHIC CORRESPONDENCE. _Mr. Wilkinson's Mode of levelling Cameras._--As you have done me the honour to notice my simple invention for levelling cameras, which I have since had an opportunity of trying in the open air for a week, and find to succeed perfectly, I wish to correct some errors which appeared in the _Photographic Journal_, from which you copied my remarks, and which arose from the notes being taken down from my verbal observations. The first part is perfectly correct but after l. 9. col. 2. "N. & Q." (Vol. vii., p. 462.) it should read thus: "The other perpendicular is then sought for; the back or front of the camera being raised or lowered until the thread cuts the perpendicular lines drawn upon the sides of the camera. By this means a perfectly horizontal plane is obtained, as true as with the best spirit-levels, and in less time. By tying three knots in the silk at twelve inches distance from the one bullet and from each other, we have a measure for stereoscopic pictures; and by making the thread thirty-nine inches and two-tenths long from one bullet to the centre of the other, we obtain a pendulum vibrating seconds, which is useful in talking portraits; as it will continue vibrating for ten minutes, if one bullet be merely hung over any point of suspension." Thus we obtain a levelling instrument, a chronometer, and a measure of distances, at a cost considerably under one penny. The above will more fully explain to your correspondent [Phi]. (Vol. vii., p. 505.) my reasons for the length of thread stated; and with respect to the diagonal lines on the ground glass, it is not material what may be the distance of the principal object, whether six feet or six hundred: for if the cross lines, or any other lines drawn on the glass, cut the central object in the picture at any particular part--for example, the window of any particular house, or the branch of any tree,--then the camera may be removed to higher or lower ground, several feet or inches, to the right or to the left, and the same lines be made to cut the same objects, previously noted; the elevation will then be the same, which completes all that is required.