674 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



thirty drops of nitric acid, and let it boil one hour, then remove the flask 

 from the fire, add eight ounces of alcohol, and bottle it. 2d. Make a solu- 

 tion consisting of one ounce of caustic soda, and twenty-five ounce sof 

 distilled water. Let it settle until clear, but do not filter it. 3d. Make a 

 Bolution of one ounce of nitrate of silver and ten ounces of distilled water. 

 4th. Concentrated aqua ammonia. The silvering fluid is made by adding 

 to three ounces of preptiration number three, sufiicient of number four to 

 re-dissolve the precipitate formed, which will be from one to two ounces, 

 add five ounces of number two, and eight ounces of distilled water. 



Clean the glass to be silvered, perfectly; the method practiced by pho- 

 tographers is as good as any. Mix for use four ounces of the silvering 

 fluid with two drachms of number one; place the glass in a convenient ves- 

 sel, and pour in this fluid in sufficient quantity to cover it. Heat the ves- 

 sel, if large, in a water bath; if small, by holding it over a fire. In a short 

 time the color of the fluid will change to a dark brown, then to a black; 

 ■when the silver is properly on the glass, little bunches of silver, not 

 deposited, will be seen rolling about, while the liquor will be quite 

 clear. The glass must now be placed in pure water and carefully rinsed, 

 when a brilliant coating of silver will be found over the whole surface. 



Light Draft Gun-Boats. 



Mr. Norman Wiard, by invitation of the chairman, gave the following 

 description of the gun-boats being built by him for the United States Gov- 

 ernment: 



These boats are light army boats, 160 feet in length and 35 feet broad, 

 and made to draw only thirty inches of water when loaded, and will have 

 a speed of about twelve miles an hour. The guns are furnished with solid 

 carriages, and the boats being double-enders, the pivot guns can be fired 

 from either end. They are also furnished with six launches, and these are 

 armed with a 12-pound rifle-gun. They have in addition to the rifle-gun a 

 field carriage, which, on arriving at a favorable place, can be taken on 

 land. The launches are intended for shallow bays and inlets, where the 

 large gun-boats could not go. Most persons who have travelled on the 

 railroad between Philadelphia and Washington, have noticed that a great 

 portion of the road is built upon trestle work, and not only this road, but 

 several others throughout this country are so constructed. The railroad 

 between Savannah and Charleston is largely built in this manner, so if 

 these gun-boats are run up as far as navigation will permit, then these 

 launches can be made to ascend still further, and if expedient, land 

 the field carriages and destroy the railroad. The guns by which these 

 boats are armed are made of steel, manufactured by myself, as is everything 

 connected with these boats. Engines, guns, harness, are all made at my 

 shops. The guns weigh 780 pounds, and are of 3-inch calibre, and might 

 be called naval howitzers. The engines are high pressure, and there are 

 surface condensers used, which, as far as I have been able to learn, have 

 been entirely successful. One of the objections to surface condensers, par- 

 ticularly in gun-boats, is, that they have to carry a great weight of water 

 in order to be effective; but in these boats I put the tubes on the outside 



