MECHANICS AND USEFUL ARTS. 75 



sheathing. The latter was perfectly clean, but astonishment was 

 caused by the galvanic action which had been induced between the 

 iron and the sheathing. The lower tier of iron plates each fifteen 

 feet in length, three feet two inches in breadth, and four and one-half 

 inches in thickness were perfectly honey-combed, the holes varying in 

 depth from one-fourth to five-eighths of an inch. Judging from the rate 

 at which the corrosion had proceeded, the plates would have been entire- 

 ly dissolved, had the vessel remained in the water many months longer. 

 It had been supposed that wooden vessels could be built with iron plat- 

 ing descending below the water-line, and that their bottoms could be 

 sheathed with copper, and thus remain as clean as copper-bottomed 

 wooden vessels. Indeed, this very mode of constructing war vessels 

 has been advocated by a French naval architect as being superior to 

 all others, and several French and Italian arnior-clads have been built 

 upon such ideas. The practical and expensive experiment made with 

 the Royal Oak affords us evidence that copper, or copper alloys, can- 

 not be employed with safety connected by sea-water with iron on a 

 vessel. The connection of these two metals forms a galvanic battery 

 leading to the rapid .decomposition of the positive metal. Scientific 

 American. 



Conflict between the WeeJiawken (Monitor) and Atlanta, Iron-Clach. 

 Some important information respecting the offensive and defensive 

 powers of iron-clad vessels and their improved armaments has been 

 derived during the past year from the conflict between the Weehawken, 

 one of Ericsson's monitor iron-clad vessels, and the iron-clad Con- 

 federate steamer Atlanta, which resulted in the surrender of the latter. 

 The Atlanta was originally a sea-going steamer, the Fingal, re- 

 modelled and iron-plated. Her armor is described as follows : First 

 and on the outside were wrought-iron bars, six inches wide by two 

 inches thick, running perpendicularly with her side, and proper- 

 ly secured, both above and below, by rivets and bolts. Across these 

 bars, horizontally, and on the inside, ran bars of like material and pat- 

 tern, fastened to the outside layer by the strongest rivets. Within this 

 layer, and fastened to it, were two thicknesses of live oak two-inch 

 plank, also running perpendicularly and horizontally, and again, within 

 these, were two more similar thicknesses of Georgia pine plank, form- 

 ing the last series of her armor. The thickness of the Atlanta's armor, 

 therefore, was twelve inches, four of iron, four of live oak, and four 

 of pine planking. Her pilot-house is also thus described : Forward . 

 of the snioke-stack was an elevation on the top deck, to all appearance 

 like a cone ; upon this cone was a small, square lookout, just large 

 enough on the inside to allow a man's head to turn with freedom. On 

 each side of this lookout were two small apertures, in the shape of 

 parallelograms, slanting toward the interior, and presenting to the pi- 

 lot's optics, in the lookout, two lookouts, an inch and a half long by an 

 inch wide. This look-out was of wrought iron, four inches thick, and 

 the cone upon which it stood was the same thickness, with this addi- 

 tional strength, however, that the interior of the pilot-house being 

 square, the interstices between the sides of the upper part of the pilot- 

 house and the concave surface of the cone were filled with eight-inch, 



^ 



square, live-oak blocks. From the top of the lookout to the base of 

 the cone was but two feet and a half. 



