The slabs that were used here were 2" × 6" × ½" and the first operation was to cut from these round disks a little larger than the finished lens. This was accomplished in the following manner and is illustrated in Fig. 1. In the chuck of a drill speeder on a Barnes drill press was placed a ¼" steel rod which carried at its lower end a copper tube, A, which was steadied at the bottom by a steel washer, bored to a loose fit to the tube, and clamped to the glass as shown. Number 40 Carborundum was used and lubricated with _plenty of water_. The tube must be lifted frequently to allow the abrasive to flow to the cutting edge. This is done so often that it seems almost a continuous motion of lifting and pressing down again, the tool resting on the glass hardly more than two or three seconds at a time. The cutting may be done at such a speed as to allow of a slight heating. As soon as the tube has cut itself about a sixteenth of an inch into the glass, the guiding washer may be removed and the glass will then act as its own guide. A disk about one inch in diameter and a half of an inch thick could be cut out in a little over a half of an hour. At B Fig. 1 is shown one of the uncut slabs and at C and D two that are about used up. Though working rather slowly this proved quite satisfactory though wasteful of glass as it cut a rather wide scarf, copper must be used; brass was tried but the wear was so great as to render it almost useless while the copper shows almost none. As these disks are cut out they are not only cone shaped but the edges are very rough so that the next operation was to grind these to smooth and true circular disks. This was done on a Wells tool grinder shown in Fig. 2, which was slowed way down by placing a large pulley on the counter shaft. The glass to be ground was held by cementing it with pitch onto a piece of brass rod which in turn was held in the drawing collet of the head A. A special wheel B, made by the Norton people for grinding the rims of spectacle lenses, was used and the machine slowed until the wheel would keep wet when running against a sponge, C, resting in water. The glass disk was in this way kept dripping and heating entirely prevented. The grinding was then carried out just as with any other material and the edge was made beautifully smooth and true in a few minutes. The beauty of pitch as a cement for holding the glass is that a slight heating will soften it so that the disk can be shifted to any position and then a dash of cold water clamps it in place and at the same time the pitch will slowly yield to the slightest pressure so that in a few minutes the glass is entirely free from strain. In manufacturing this sort of work is done with a diamond and is of course done much more quickly.