UNDERGROUND RAILROAD—A company has been organized in London to tunnel from the Post Office to the marble arch entrance on Hyde Park. Mr. Hawkshaw, the engineer of the proposed line, states that it shall be constructed without any interruption of the street traffic between the hours of six in tho morning and ten at night. Any diggings made during the night will be covered in, and the paving replaced before six in the morning. The trains are to be drawn by wire ropes j from fixed engines at each end, so that the air of the tunnel will not be poisoned by the smoke and vapors of locomotives; and, as there can be no collisions, trains will start every two minutes. In the opinion of competent engineers, the substitution of locomotives for ropes was a mistake, whether regarded from the scientific or the economic point of view. The proposed new tunnel road will have nine stations, and the estimated cost is seven million dollars. Improved means of communication in cities is one of the greatest necessities of the day. We want, if possible, to get rid of the surface roads- THB STBAMBE PBEBIEE.—The salvation of the French steamer Pereire from utter destruction upon the occasion of the accident in the recent attempted voyage from Havre to I New York, seems little less than a miracle. On January 20th she encountered a tremendous hurricane, and at about two oclock on the following afternoon, an immense wave formed of about seven hundred tuns of water, fell like an avalanche on the deck. Twenty-four out of the thirty-six furnaces were extinguished, four persons were killed, and twenty-one seriously injured. Some of the fatal accidents took place on deck. One young lady was killed while reading in the saloon —the water struck her on the back of the neck, and broke the spinal column. That the steamer was saved and brought back to port after shipping this immense wave, speaks vol- I umes for the staunchness of her construction. GOOD TESTIMONY.—W. Haddon Marriott, of Baltimore, writes us as follows: When I reached home this evening I was agreeably surprised to find awaiting me my letters patent, which upon examination I find to be in every particular satisfactory, and therefore, I must tender you my sincere thanks for the promptness, uprightness, and thorough ability which you have shown in executing the trust confided to you. I shall not only recommend you to such of my friends as need your invaluable advice and assistance, but shall deem it a prixilege to be able to point them to honest, upright men, so rare now-a-days, who will not betray their confidence. To show my confidence in you, I am about to place in your hands another, I think, far more valuable case, trusting to your justly given and undisputed ability. PAINTING ZINC.—A difficulty is often experienced in causing oil colors to adhere to sheet zinc. Boettger recommends the employment of a mordant, so to speak, of the following composition : One part of chloride of copper, 1 of nitrate of copper, and 1 of sal-ammoniac, are to be dissolved in 64 parts of water, to which solution is to be added 1 part of commercial hydrochloric acid. The sheets of zinc are to be brushed over with this liquid, which gives them a deep black color; in the course of from 12 to 24 hours they become dry, and to their now dirty gray surface a coat of any oil color will firmly adhere. Some sheetB of zinc prepared in this way, and afterwards painted, have been found to entirely withstand all the atmospheric changes of winter and summer. COPPEE SMOKE.—The smoke from the copper-smelting works of Swansea, Wales, has long been a nuisance to the neighborhood, and the frequent occasion of litigation. Mr. Vivian, one of the principal owners, has at length devised a plan for condensing the sulphureous vapors, thereby converting them into oil of vitriol. This discovery will restore to agriculture thousands of acres of land which the noxious vapors have rendered sterile, and will relive the inhabitants of the murky cloud which has nearly smothered them. The oil of vitriol thus manufactured will be useful, in the preparation of the compounds necessary to redeem the land from the unfruitful state into which it has fallen. Two lads of this city, aged respectively 8 and 10 yeare, who recently mounted the cow-catcher of the locomotive Leonard W. Jerome, intending to take a short ride along the Eleventh avenue, supposing the engine would stop after moving a short distance, were carried to Peekskill, forty miles away. They were in a position where the engineer could not see them,and upon their arrival at Peekskill, one of them fell off upon the ground senseless, and the other was too weak to walk. After being cared for, the boys were returned to this city. We venture to say they will hereafter give the cowcatcher a wide berth. TEEMPEBB VELOCIPEDE.—In another column we publish the illustration and description of the above velocipede. The inventor says he is 69 years old and that he can ride his machine an hour or two with a good walking motion, reading the SCIENTIFIC AMEEICAN, with comfort, and turn inside a circle four feet diameter, steering with one foot only. The machine can be used as a one-wheeled velocipede; that is, with the rider over the driving Wheel and the hind wheels used only as steadiers. THE contrast between the mildness of the winter in the United States and elsewhere, and the violence of the storms at sea, is attracting attention. IB there any connection between these phenomena ? If any other than the universal law of J compensation throughout all the operations of nature, what is it?