M. A. AINSLEY

We have now arrived at the point where the worker will begin to appreciate the real difficulties of the work. Up to this point all has been fairly easy; but the beginner must not be discouraged if bis early a1-tempts at the construction of polishers are failures, and he must be prepared to exercise unlimited patience. The pleasure of seeing the wonders of the heavens through a telescope of his own construction will amply repay him for his time and trouble.

The pitch used, as before recommended, should be Swedish pitch, in 2 lb. boxes - about 2 lbs. will be required. Also we must obtain some rouge. I got mile in 1/4 lb. packets through a jeweller, who specially ordered it for me, and it is important to get the very best that can be got. If there is any difficulty about it, an optician would probably be able to supply it. It is somewhat expensive - $2.50 the pound, or so - but 1/4 lb. will be ample. An iron ladle to melt the pitch and an iron spoon to stir it are, of course, necessary, and an ample supply of turpentine.

There are two distinct methods that I have tried of making the polisher: One is to pour the pitch directly on the tool and stamp grooves in it to form the necessary facets. The other is to make the squares of pitch separately and mount them independently on the tool. I (prefer the latter method, if only because a slight flaw in the polisher does not necessitate the renewal of the whole thing - local repairs being quite easy.

Now pitch is, as I have said, a good friend but a bad enemy. As I was told by an expert correspondent: "Stick to pitch - it will certainly stick to you," and "if it is a good friend, it does sometimes stick closer than a brother. " But I am glad to say that there is one thing that pitch does not show any brotherly affection for, and that is blotting-paper. Provide, therefore, an ample supply of blotting-paper in sheets not less than 10 in. square, if possible. A large sheet of plate-glass or marble 14 in. square should be provided, and we shall require a stamper to form the square, and a frame of wood to retain the pitch till cool. The frame should be, for a 6 in. mirror, 40 in. square inside and 12 in. outside, the sides being therefore 1 in. broad, and it should be 3/8 in. deep. For a larger mirror it should, of course, be larger, the inside measurement being about 1 in. larger than the diameter of the mirror. This is to allow for a few extra squares in case any get broken. The stamper is made by screwing two flat pieces of wood, 12 in. x 1 1/2 x 1/4 in. to the sides of a rod 1 in. square and about 18 in. long. The ends of the rod may be rounded off to form handles, and the flat side pieces shou'd project about 1/2 in. as shown in the figure, and have V-shaped edges. I append a rough sketch of the instrument, which will explain what I mean.

The hardness of the pitch is a matter of some importance, and authorities differ to a large extent. I found in my own case, that if a shilling, standing on its edge, left five complete impressions of the "mill " in one minute, it was about right; the temperature makes a difference, the pitch being harder when cold, so that the test should be carried out at the same temperature as that of the room in which it is proposed to work. I do not recommend the beginner to have his pitch any softer than I have indicated; it may be even a little harder.

The pitch having been melted as before directed (in my second letter), its hardness should be tested by pouring a little on a piece of glass; and turpentine should be added slowly till it is about right, the pitch being thoroughly and constantly stirred while the turpentine is added. If too soft it should be kept at the meltiug point and allowed to evaporate, when it will harden. But I did not find this necessary, as the pitch is now poured out steadily on to the slab till it has a depth rather less than that of the frame, say 5-16 in. Any impurities must be kept back with the iron spoon.

After it has cooled down a bit, but before it hardens - and this may be tested by touching it it with a blunt wooden point covered with wet blotting-paper - the frame may be removed. This is quite easy if the blot ing-paper is used, but not so easy if it is omitted - and a cake of pitch 10 in. square by 5-16, is left.

We now bring the stamper into action. A series of grooves are stamped out parallel with one side of the pitch cake. Each groove is stamped twice, the following edge of the stamper being placed in the groove just vacated by the leading edge. In this way the squares are all kept of the same size. A similar set of grooves at right angles to the first are stamped and the pitch cake is then divided in 1 in. squares separated by 1/4 in. grooves. It is protected from dust without, of course, being touched, and left to get thoroughly cold. When cold it is slid to the edge of the glass slab and broken into squares very much as if it were toffee or chocolate. After a little practice this can be done without splintering the squares if care is taken; but as there are plenty of squares made, the loss of a few does not matter. The hands and pitch must be kept wet, to avoid the latter sticking to the fingers; and the pitch squares, when broken off, should be placed in a basin of cold water till required.