L.G.C.H.—­1.  In soldering, the edges of the metals to be put together must be perfectly clean, to insure which, as well as to counteract the oxidization which most metals undergo when heated, a flux is used which neutralizes these otherwise serious impediments, securing a firm joint.  Borax, rosin, sal-ammoniac, common salt, limestone, glass and several other substances are used for this purpose, according to the nature of the metal used.  Rosin or oil is usually employed in soldering tin and lead, while a mixture of muriate of zinc and sal-ammoniac is used with steel. 2.  A complete outfit for printing an amateur paper such as that you describe will cost at least $200, and can be purchased from any dealer in printing materials. 3.  Construct the camera according to the plans laid down in Vol. 9, No. 34.  The cost of that issue will be 6 cents, postage free.

J.H.R.—­Numerous articles on how to construct cabinets, bookcases, etc., have been published in previous volumes of this paper.  Among these are the following:  “How to Make a Refrigerator,” “Cabinet-Making for Beginners” and “Screens and How to Make Them.”  Nos. 35, 47 and 48, Vol. 5; “How to Make a Desk,” “Hanging Bookshelves” and “Corner Cabinet,” Nos. 7, 15 and 22, Vol. 6; “Hanging Cabinet,” No. 16, Vol. 7; “How to Make an Amateur Carpenter’s Bench,” No. 36, Vol. 8; “How to Make a Portable Bookcase,” No. 2, Vol. 10, and “How to Make a Bookcase and Cabinet,” No. 8, Vol. 12.  These numbers will cost six cents each, no charge being made for postage.  It is our intention to publish such articles in this and succeeding volumes, whenever the opportunity is presented of giving the boys novel and useful ideas in the “how to make” line.

M.S.S.—­1.  The sun’s average distance from the earth is about 93,000,000 miles.  Since the orbit of the earth is elliptical, and the sun is situated at one of its foci, the earth is nearly 3,000,000 miles further from the sun in midsummer than it is in midwinter in the northern hemisphere.  In the southern hemisphere, these conditions are exactly reversed. 2.  U.S.  Senators are elected by the legislatures of the States they represent, while members of the National House or Representatives are elected by the people. 3.  It is not considered improper to write a short message or letter on a half-sheet of paper; in fact, some styles of writing paper consist of but a single sheet. 4.  The use of a moderately stiff tooth-brush, clean water and castile soap will keep the teeth white and in good condition.  Tooth-powders are injurious. 5.  Nickel-plating should not be exposed to dampness, and must be kept bright by wiping with a soft rag.