(33) S. C. D. says: Please give directions for electrotyping cylindrical rollers for impressing upon sheets of wax, accurately, of the proper figure for honeycomb foundations. The figure for the surface of the cylinders to be derived from sheets of wax foundation, having the figure correctly impressed upon them. A. This can be done by coating with plumbago, and then electrotyping with copper, in a way familiar to most printers and to all electrotyping establishments. The plates can afterwards be bent round a roller, and used to impress the sheets of wax. (34) J. H. T. asks: There is a piece of ground, 100 rods long and 10 rods wide at one end, running to a point at the other, which we wish to divide into 4 equal lots. Please give a rule. A. Let the 100 rods be the base of a triangle, divide it into 4 parts of 25 rods each, and join the apex with each of the three dividing points. You will then have 4 triangles on equal bases and between the same parallels, which, according to Euclid, are equal to each other. (35) R. S. asks: What are the chemical qualities of bisulphide of lime, and how can I prepare it? A. The bisulphide of calcium (C_{2}S_{5}) is produced by boiling milk of lime with sulphur and water, but not long enough to allow the lime to become completely saturated. The filtered liquid, on cooling, deposits crystals whose composition agrees with the formula C_{2}S_{2} + 3H_{2}O. Exposed to the air, it soon absorbs oxygen, becoming converted into insoluble sulphate of calcium. Its aqueous solutions are likewise decomposed. Its reactions with the metallic salts are similar to those of the alkaline sulphides. (36) H. M. S. asks: 1. Of what is the bronze preparation made and how is it applied to clock fronts? A. Bronze powders are made of various metallic alloys. The gold bronze is usually made of Dutch gold (an alloy of copper and zinc) and of the bisulphide of tin (_aurum musivum_). They are usually applied to metal work by means of an oil size or japan varnish. 2. In what way can I remove the old bronze? A. Wash first with a solution of washing soda (hot), clean and dry, and then rub with a little benzole, alcohol, or ether. (37) W. E. W. asks: 1. Of what mixture is the bright red paint usually put upon axes made? A. It consists of fine vermilion ground with 1 part boiled oil and 2 parts turpentine. 2. Is more than one coat applied? A. One coat will suffice. It is best applied with a fine brush, when the metal is warm. (38) C. M. B. asks: Is the odor emitted by the ailanthus tree unwholesome? A. It is considered so by many, but we have no proof as to the facts. (39) L. S. & Co. ask: Is there anything known which would clean the hands from paints and lacquers without the use of turpentine? A. A little ammonia and benzine or naphtha, aided by a little sand, is often used in stubborn cases; put plenty of good soap and warm water, with a stiff brush or a small piece of pumicestone, will ordinarily suffice.