Speaking makes the ready man, writing the correct man, and reading the full man. * * * * * PRESERVATION OF IRON. BY PROF. HENRY E. COLTON. "What is wanted is something equally applicable to large or small pieces of iron, and which will answer to ward off the attacks not only of the common atmospheric oxygen, but also remain unaffected by acids or salt waters." The above from a late number of the SCIENTIFIC AMERICAN states not only the writer's ideas but also one of the greatest wants of the age. Iron is daily being put to more and more varied uses. On land the great question is what will prevent rust; on water, what will prevent rust and fouling of bottoms of iron vessels. We will briefly summarize the many patents granted for this purpose. Eight are for sheathing of various kinds put on in varied modes. The most practicable of these is a system prepared by Daft. Most iron vessels are now constructed by every other plate lapping the edges of the one between. He proposes, instead of having the plates all the same width, to have one wide and one very narrow plate. This would leave a trough between the two wide plates of the depth of the thickness of the plates. He proposes to force into this trough very tightly pieces of teak, and to the teak, thus embedded, he nails a sheathing of zinc. The zinc is kept clean by slowly wearing away of its surface from action by contact with the iron and salt water. There are four patents, in which various, so-called, non-conducting coats are put on the iron, and copper pigment in some form put on over them. These have been specially condemned in England, as no matter how good the non-conducting substance--and many are so only in name--it will become rubbed off at some points, and there the bottom will be eaten both by salt water and action of copper. Coal tar and asphaltum are the subjects of patents in various forms. One patent claims rubber or gutta-percha dissolved in linseed oil as a vehicle in which to grind the pigment; another the same dissolved in naphtha or bisulphide of carbon as a pigment; another hard rubber, ground. Enameling with different materials is proposed by some, while one proposes to glaze the bottoms so that barnacles and grass would find a slippery foothold. Combinations of tallow, resin, and tar--mineral and pine--are patented mostly to use over other paints. Coal tar, sulphur, lime, and tallow, are the subject of one patent; guano, red lead, and oil of another; while sulphur and silica are claimed by a third. Paints containing mercury, arsenic, and even strychnine, are the subjects of several patents. A mixture of coal tar and mercurial ointment of one. Galvanism is proposed to be used in various ways--strips of copper and zinc, or by galvanizing the plates before use. Black lead finds a place in many compositions.