Page:The American Cyclopædia (1879) Volume XIV.djvu/884

 858 SHIP were most conclusively established when the yacht America, built on the same principles, carried off the prize in 1851 in competition with the English yachts that had confident- ly challenged the world to a trial of speed. From these schooners the step was natural to the famous clipper ships by the adoption of the square rig for larger vessels of similar model. They were called into existence by the increasing importance of the East India trade, in which speed and punctuality were more essential than mere stowage capacity, and still more by the sudden springing up of the Cali- fornia trade with its immense passenger traffic. In vessels of this class the voyage round Cape Horn lost its terrors, and the passage from New York to San Francisco was confidently calcu- lated within a few days, and this at hardly half its former length. The clipper ship Great Republic, built by Donald McKay of East Bos- ton, was an excellent type of this class, and was the largest, if not the fastest, merchantman ever constructed. Her capacity was about 4,000 tons, and her original dimensions were 325 ft. length, 53 ft. width, and 37 ft. depth. A peculiar feature in her model was the rising of her keel for 60 ft. forward, gradually curv- ing into the arc of a circle as it blended with the stem. She had four masts, all provided with lightning rods. The after one, called the spanker mast, was fore-and-aft rigged, of a single spar; the others were built of hard pine, the parts dowelled together, bolted and hooped over all with iron. The main yard was 120 ft. long. A single suit of her sails con- sisted of 15,653 yards of canvas. Even in 1851 the performances of some of the clipper ships on long voyages were far superior for days together to those of the steam vessels of that time, and on the whole run hardly infe- rior. In that year the Flying Cloud made the passage from New York to San Francisco in 89 days and 21 hours. Her greatest distance from noon to noon of any day was 874 knots (433} statute miles), which, allowing for dif- ference of longitude, was made in 24 h. 19 m. 4 sec., or at the rate of 17*77 m. an hour. In 1852 the Comet arrived in New York from San Francisco in 83 days, and the Sovereign of the Seas from the Sandwich islands in 82 days. The greatest distance made by the latter from noon to noon in any day (in this case 23 h. 2. m. 4 sec.) was 362 knots (419 in.), or at the rate of 17'88 m. an hour. From March 9 to March 31, from lat. 48 S. in the Pacific to 36 S. in the Atlantic, the ship made 29 of latitude and 126 of longitude, equal to 6,246 statute miles, or a daily average of 283*9 in. During 11 of these days consecutively her daily average was 354 m., and during 4 consecutive days 898} m. Her daily average for the whole distance of 17,597 m. was 222-7 statute miles, or at the rate of over 9 m. an hour for 1,896 consecutive hours. The two prominent features that con- stitute the essential improvements of modern times are the shape of the bow and the in- creased length of the vessel. In place of the convex form noticed in the older ships in tra- cing the lines from the stem aft along and be- low the water, is now substituted a concave surface giving to the bow the shape of an elon- gated wedge slightly hollowed on the face, by which the waters are more easily parted and thrown aside. This wedge shape is ex- tended even to beyond the centre of the ship, so that the broadest part, instead of being as formerly one third the distance from the bow, is now about the same proportional distance from the stern. Above the water line the old proportions may still be retained. This form of bow is not by any means altogether new, having been adopted by the Spaniards in past times and by various barbarous nations for their small craft ; but its merits not being ap- preciated by other European nations, it was sacrificed for the sake of greater stowage, es- pecially by the English, who were the more impelled to this course by reason of the old tonnage laws, in force up to 1836, as regards the method of measurement for regulating the dues, the increase of capacity gained in the bow not being reckoned in the estimate. Thus the round swelling bow became the established form, in the correctness of which the builders felt confirmed by the sfmilar shape in the head of the whale and of the codfish. The hol- lowed lines drawn from the stem back on each side the ship were designed by Mr. Scott Rus- sell from his observations made as far back as 1832 upon the shape of the wave set in mo- tion, as by the influx of water from the dis- charging of a lock of a canal, which travels at rates corresponding to the depth, as 8 m. an hour for 5 ft. depth, 10 m. for 7 ft., 15 m. for 15 ft., 18 for 20, 20 for 30, 25 for 40, and 30 for 50. Hence he designated them wave lines, and the form of the bow they produced he called the wave form. The lines for the stern he also established by study of the refilling or replacing or following wave, as necessarily fulling in cycloidal curves. Definite lengths indicate definite rates with a given power, and it would be impossible to force a ship through the water at rates much exceeding those indicated as adapt- ed to the length of her lines without an ex- travagant expenditure of power. Additional length of body inserted in the centre seems to have no effect, except as it presents an increased surface for adhesion of the water. Thus the old idea that there must be a certain proportion between the length and breadth of a vessel, as that which for a long time was adopted in prac- tice of one fourth the length for the breadth, proves to be entirely false. The speed does not appear to be affected by the shape of the vessel across her middle or her midship section, nor by differences of depth to a considerable ex- tent. The proportion between the speed for which a ship is to be designed and the length of entrance and run, Mr. Russell states to be three fifths of the whole length for fore body