An old paraffine cask was what I used; but it was not high enough for me, as I stand 6 ft. 2 in., so I raised it another 6 in. or so by means of a stout box, which should be as flat as possible, to keep the tool in place. I found this quite steady, though I think it would be better still to fill both box and cask with stones, earth or something heavy enough. The surface of the tool was high enough to be about 5 in. below the point of my elbow when standing upright. This gave command of the work and avoided stooping, while I could put sufficient pressure on the mirror during grinding to make the emery do its work. I did not find it necessary to fix the tool down (with pitch or otherwise), and if there was any flexure of the tool during the work, it has no perceptible effect on the figure of the completed mirror. The same tool was used to grind both mirrors; the second mirror, however, seemed to be quite rigid enough to impart a good spherical figure to the mirror.