be smoked. Light your tapers or your oil torch, and turn the plate upside down. Allow the flame just to touch the plate, and keep moving it about rapidly, so that it may touch all points of the plate, without remaining long at any one of them. If this precaution is ignored, the ground will be burned, with the result before stated. The smoking is finished as soon as the plate is uniformly blackened all over, and the glimmer of the metal can no longer be seen through the ground. Now allow the plate to cool so that the ground may harden. Avoid dust as much as possible while grounding and smoking the plate. Particles of dust embedded in the ground may cause holes which will admit the acid where you do not wish it to act.

5. Points or Needles.—The plate is now ready for drawing upon it, but before you can proceed to draw you must prepare your points or needles. Two will do for this first experiment, a fine one and a coarse one. For the fine one you may use a sewing-needle, for the coarser one a medium embroidery needle, both set in wood so that the points project about a quarter of an inch. If you are going to use rat-tail files, grind the handle-ends on your oil-stone until they attain the requisite fineness. Hold the file flat on the stone, so as to get a gradually tapering point, and turn continually. See to it that even the point of your finest needle is not too sharp. If it scratches when you draw it lightly over a piece of card-board, describe circles with it on the board until it simply makes a mark without scratching. The coarse needle must be evenly rounded, as otherwise it may have a cutting point somewhere.