snip 859 and two fifths for after body. For a speed of six statute miles an hour the length of entrance should be, according to his rule, 15-12 ft., length of run 10-8 ft. ; for 8 m., 26-88 ft. for entrance and 19*2 for run ; for 10 m., 42 and 30 ; for 15 m., 94'50 and 67'5 ; for 20 m., 168 and 120. The great experiments of the Eng- lish in the construction of their largest steam- ers have been made on these principles. Be- fore their adoption it was taught by the most experienced ship builders, and in this opinion Mr. Scott Kussell was himself educated, that it was impossible to force steamboats through the water at a greater rate than 9 m. an hour. He had even seen engines of 50 horse power taken out of one of the short bluff -bow steam- boats, and replaced with others of 75 horse power, with the effect of increasing her speed only about a quarter of a knot an hour. With the increased power the resistance in front was much more than proportionally increased, keeping down the speed in this instance to about the same amount. This was in accor- dance with the mathematical deduction of the resistance in passing through water increasing as the squares of the velocities, or nearly so, and the power necessary to impart an increased velocity varying nearly as the cube of such in- creased velocity. It is not strange therefore that the opinion prevailed, that if a rate of 12 or 14 m. could ever be attained in sea-going steamers against the enormous resistance, in- creased as it must be by the tremendous shock of opposing waves, no vessel could be strong enough to complete a voyage. Yet in the United States the fallacy of these views had been practically demonstrated in the steam- boats on the Hudson river for several years before the principles of their success were recognized by the English ship builders. In 1827 these boats were making the trip from New York to Albany in 12 hours, the distance being about 145 statute miles, and the trip usu- ally including 12 stoppings, at six of which the boats were brought to and fastened to the wharves. Several crossings of the river also added to the distance and the time over a trip direct. In 1829 the passage had been accom- plished in 10^ hours, in 1831 in 10J- hours, and in 1832 in 9 h. 18 m. (See paper by William O. Redfieldin "American Journal of Science," vol. xxiii., 1833.*) These boats were long and sharp, furnished with " cut-water bows," and of dimensions in some instances as follows: length 233 ft., breadth of hull at the water lines 28 ft., depth of hold 10 ft., draught of water 44 ft. ; length 180 ft., breadth at the water line 28 ft. ; length 220 ft., breadth 25 ft. ; and length 145 ft., breadth 27 ft. In 1832 Mr. Eussell demonstrated theoretically the pnnci-
- Since the publication of the paper by Mr. Edfleld still
increased rates of speed have been attained by these boats, till, in October, 1860, the steamboat Daniel Drew made trip in 6 h. 50 m., including in this five landings and sever* crossings involved by them : these may fairly be considered aa consuming 50 minutes, thus making the rate 24 m. an hour, the highest speed ever recorded upon the water. pies upon which such speed was attainable, and in 1837 a river steamer called the Ves- per, built on the lines he recommended, was actually run on the Thames at about 12 m. an hour. The direction in which improvements in the construction of fast ships were to be made being thus determined by theory and practice both in England and the United States, an active rivalry sprang up between the two nations, each producing almost every year steamers of surpassing excellence. But the American government refusing to pay subsi- dies to steamship lines, the scale turned in fa- vor of the English, whose resources were great- er in other respects than those of the Ameri- cans. This was especially apparent when in the course of the contest it was discovered that a limft was encountered to the required elongation of the ships, from the want of strength in wooden timbers, however large and well put together, to bear the increased strain ; and that resort must be had to iron plates riveted together, the suitability of which for such use was fully established by the suc- cess of the Britannia bridge. In 1855 the Cunard iron steamer Persia was constructed, of 360 ft. length of hull, 45 ft. breadth, and 32 ft. depth, and of capacity exceeding by 1,200 tons the largest of the other ships of the same line. The next of these grand attempts was the construction of the Great Eastern, in which the principle was put to an extreme test upon a length of hull of 680 ft., a breadth of 82 ft., and a depth of 58 ft. Her lines were designed by Mr. Scott Russell in exact con- formity with his theoretical wave lines. Those of the bow are 330 ft. in length, and the length of the run is 226 ft., the filling in of parallel body to afford the capacity wanted being 120 ft. This middle portion, as already remarked, is supposed to have no effect so long as the length in other respects is sufficient for attain- ing the required speed with the given power. In this case the power furnished could be ex- pected to give only 15 m. an hour, and this she attained. For further account of the use of steam in navigation and the history of this ap- plication, see STEAM NAVIGATION. The sub- stitution of iron for wood in the construction of vessels was first made experimentally i 1821, but did not come into practical use till 1829-'30. In these years the late John Laird of Birkenhead built some iron cargo lighters at his works there, where the business of iron ship building has since been uninterruptedly con- tinued and upward of 400 iron vessels have been completed. In 1830-'31 the late Sir William Fairbairn built a small iron steamer at Man- chester, and he afterward constructed at Mill- wall many steamers of the same material. In France and in the United States iron has been partially introduced into wooden ships, bars of iron being employed to great advantage for a diagonal bracing covering the inner face of the timbers with a complete network ; horizontal stringers of plate iron are also fas-
