MECHANICS AND USEFUL ARTS. 23 



seven inches in thickness; the keel block being just double this size. The 

 blocks were cast overboard, and the rope which was attached to them was 

 passed around the bow and underneath the bottom of the vessel, and by 

 hauling upon the ropes alternately the scraping brought off a large quantity 

 of dirt. 



Five men were employed in the operation, which seemed quite easy. 

 The pressure of the water kept the blocks close to the vessel's side, while 

 the lightness of the materials added much to the rapidity with which the 

 apparatus performed the work. As rapidly as the part of the vessel on 

 which the apparatus was employed was cleaned, the men moved a few 

 inches aft, until the whole bottom was thoroughly scraped. When the 

 sharp curves of the vessel's lines interfere with the use of the blocks, a 

 peculiar-shaped scraper, fitted to a long pole, is used, and, being floated also 

 by cork, the work is comparatively easy and rapid. 



BEACHING THE GREAT EASTERN. 



The operation of cleaning the bottom of the Great Eastern has been per- 

 formed by placing her upon a " gridiron," or framework of timber, on the 

 beach at Mil ford Haven, England. The arrangement of this construction 

 is described as follows in the London Times : 



The beach, to the distance of five hundred and fifty feet, has been exca- 

 vated and levelled to within a few feet of low-water mark at spring tides, 

 which at high water will give a depth of twenty-five to twenty-seven feet. 

 The beaching-place itself is composed of two " grids," fifty yards distant 

 from each other. Each grid is one hundred and fifty feet long, constructed 

 of forty strong transverse " baulks," or beams, of forty -five, thirty-five, 

 thirty, and twenty -five feet long by thirteen inches square. They are laid 

 down in four lots, ten of each length, with an interval between each beam 

 of three feet. Each baulk of timber is firmly fixed in its place by three 

 iron-shod piles, of from three to four feet long. The longest of these lots is 

 laid nearest amidships, and the rest according to their length, thus tapering 

 off to the stem and stern, so as in some degree to correspond with the beam 

 of that part of the ship that will be immediately above them. Two " dol- 

 phins," thirty feet in height, made of four baulks, each thirteen inches 

 square, firmly clamped and bolted together, strongly supported by back and 

 diagonal struts, have been driven in at about three hundred feet apart. 



These are for the ship's side to lie against, as well as to act as guides in the 

 actual operation of beaching. One of these dolphins will be just forward 

 of the starboard sponson, and the other near her starboard quarter. These, 

 together with the mooring tackle and other necessary gear, all of which are 

 provided, will keep the vessel in her position. The Great Eastern being six 

 hundred and fifty feet long, it will thus follow that when in position she will 

 be supported for five hundred and fifty feet of her length; viz., three hun- 

 dred on the two grids, and two hundred and fifty on the levelled beach, 

 leaving only fifty feet of her bow and stern projecting beyond the timbers 

 and excavations. The whole structure has been made at the expense of the 

 South Wales Railway Company, and will cost upwards of one thousand 

 pounds. 



IRON-PLATED SHIPS. 



The first steel-plated frigate, constructed by the French government, was 

 launched in September last. She is called La Gloire, and is a magnili- 



