February 27, 1891.] 



SCIENCE. 



119 



He had found the same kind of ruins all over the country, very 

 frequently on the summit of difficult kopjes. Those at Tati and 

 Impakwe are good exaoiples; but the most perfect, perhaps, of all 

 lies north-west of Tati. The tower there is about sixty feet in 

 length and breadth, and eighty feet high ; the walls about fifteen 

 feet thick ; and it is entered by a passage winding spirally to the 

 top, which is so arranged as to be commanded by archers from 

 the interior all the way, and is so narrow that it admits of the 

 passage of one person only at a time. 



DEVELOPMENT OF MODERN MARINE ENGINEERING.' 

 The development of modern marine engineering in tlie United 

 States may fairly be said to have begun with the construction of 

 the engines of the steamship " George W. Clyde," by William 

 Cramp'& Sons, in 1871, which were the pioneer two crank com- 

 pound engines in America. Prior to this our engineers and ma- 

 chinists had brought the simple engine to its zenith of possible 

 development, but with the advent of the compound engine that 

 era ceased to be of interest except in the historical sense. 



The discovery of the principle of expansion, and the theory of 

 the compound engine based upon it, long antedate their practical 

 application. The earliest works on steam engineering contain 

 evidences of knowledge of the principle, and foreshadow the ap- 

 plication of expansion ; but tlie compound engine as a practical 

 fact is only about twenty-four years old in England, and about 

 twenty years old in the United States. Its success as a fuel 

 economizer at once dominated the construction of simple engines. 

 and all other American ship-builders were compelled to follow 

 Cramp's lead. 



From the " George W. Clyde," in 1871, to Mr. Jay Gould's cele- 

 brated steam-yacht " Atalanta," in 1883, a period of eleven years, 

 the development of the compound engine was steadily pushed to 

 its climax of air-tight fire-room, forced draught, and the highest 

 boiler-pressure consistent with economy in double expansion. 

 This limit was reached in the '' Atalanta; " and during the inter- 

 vening period Messrs. Cramp & Sons had built about 70,000 regis- 

 tered tons of iron steam shipping, besides a number of yachts 

 and other small crafts. 



The era of double expansion terminated in 1885, with the con- 

 struction of the steam-yacht " Peerless," wliich was equipped with 

 the first triple expansion engines built in the United States. 



This remarkable little ship was built by Cramp & Sons on their 

 own account, at a cost approximating $100,000, simply as a prac- 

 tical experiment in the direction of the advance from two to 

 three expansions of working steam. The result of the experiment 

 left no room for argument as to the efficacy of the new system; 

 and, though a few merchant ships were afterwards built by them 

 with ordinary compound engines, they were merely duplicates of 

 earlier vessels, and none but triple expansion engines were ever 

 afterward designed or recommended by that firm. 



In the "Peerless," as an experimental ship, Messrs. Cramp & 

 Sons went to what has since been recognized as the upper limit 

 of economical boiler-pressure for the purposes of triple ex- 

 pansion, which was 155 pounds. The registered tonnage of the 

 " Peerless" was 228 only, but her engines developed about 1,060 

 indicated horse-power, giving her a speed of 17J knots, which 

 made her the fastest steam-yacht of her time and class. 



From the " Peerless " in 1885 to the •' Vesuvius" in 1889 was a 

 period marked by tremendous progress. In the latter vessel a 

 power of 4,440 horses was developed in 25i tons weight of ma- 

 chinery, and applied to the propulsion of about 905 tons of dis- 

 placement, the result being a speed of 21.65 knots an hour. 



During this period Messrs. Cramp & Sons also built the hori- 

 zontal triple expansion engines of the " Newark," "Philadelphia," 

 "Baltimore," and "Yorktown," United States men-of-war, to- 

 gether with about 56,000 horse-power of triple expansion machinery 

 tor merchant vessels, a compound oscillating engine for the Ston- 

 ington Steamship Line steamer " Connecticut " (with cylinders 56 

 inches and 104 inches respectively, and 11 feet stroke), — the 

 largest engine of that type ever built, and carrying 110 pounds of 

 steam-pressure, — together with several heavy compound pumping- 

 1 From The Crank. 



engines for water-works, ranging in capacity from 10,000,000 to 

 20,000,000 gallons per day. 



Advantage was taken of this school of development by the Navy 

 Department, and Chief Engineer George W. Melville was stationed 

 at the ship-yard of Cramp & Sons as inspector of machinery. 

 While serving as such, Mr. Melville designed the engines of the 

 cruiser "San Francisco," and laid broad and deep the foundation 

 of that knowledge of marine engineering which, since his promo- 

 tion to the chiefship of the Bureau of Steam Engineering, has 

 found expression in a group of machinery designs aggregating 

 over 150,000 horse-power, all of which are now in various stages 

 of construction, and classed by all competent critics at home and 

 abroad as representing advanced types of marine engineering in 

 every sense. 



The latest of Messrs. Cramp & Sons' engines brought to trial 

 are those of the United States cruiser "Newark," which are of the 

 horizontal, direct-acting, three-cylinder type. They weigh, in- 

 cluding water in the boilers, 761 tons, and developed, on four 

 hours' trial, 8,660 indicated horse-power, or 11.64 horse-power to 

 the ton of weight, which exceeds any other performance of that 

 type of machinery. 



At the present time this concern has in the course of construc- 

 tion the machinery for two 10,000-ton battle-ships, one armored 

 cruiser of 3,100 tons, and one protected cruiser of 7.300 tons, em- 

 bracing, in all, eleven engines of approximately 60,000 indicated 

 horse-power, of which three are to be placed in the latter vessel 

 to drive triple screws, and designed to produce a speed of 21 

 knots. 



It is quite generally conceded that, in the production of these 

 colossal machines, the limit of size and weight of boilers of the 

 cylindrical or tubular type has been reached ; those for the ar- 

 mored cruiser "New York '" having a diameter of 15.9 feet, re- 

 quiring a shell plate thickness of 1.33 inches, and weighing 70 

 tons each when ready for installation on board ship. 



The machinery plans for the 8,200-ton armored cruiser, and the 

 7,300 ton protected cruiser, present several interesting novelties. 

 The first named is to be powered with four engines, two working 

 on each shaft, and provided with means of disconnection so as to 

 cruise under half power under ordinary circumstances. These 

 four engines are installed in separate watertight compartments. 

 The power is 4,500 each, or 18,000 collectively, and is expected to 

 produce a speed of twenty knots. 



In the 7, 300-ton protected cruiser there are to be three engines, 

 on three shafts. Two of the engines, driving the port and star- 

 board shafts, are placed in the usual manner on twin screw ves- 

 sels. The third, driving the central shaft, is placed abaft the other 

 two, each having its own compartment. 



These are to be among the most powerful machines ever built, 

 having 7,000 indicated horse-power each, or 21,000 collectively, 

 and are to produce a speed of twenty-one knots. 



SUBMARINE GUNS. 



C. S BusHNELL of New Haven, vice-president of the Ericsson 

 Coast Defence Company, which has just had the old " Destroyer " 

 taken out of the Brooklyn Navy Yard and hauled up on Simpson's 

 dry dock at South Brooklyn for repairs, says, in the New York 

 Times, in regard to the fitting-up of the vessel for the trial of a 

 aewly invented gun, — 



"On the 'Destroyer' the late Capt. Ericsson and C. H. Dela- 

 mater spent $150,000. The vessel is 120 feet long, and is sub- 

 stantially constructed, though now in great need of repairs. Our 

 company has a capital of $250,000. We are fitting up the vessel 

 for the purpose of testing a gun that will fire under water. Now, 

 with the heavy nettings which the big war-vessels have for the 

 protection of themselves against torpedoes, the ordinary projectiles 

 are almost useless. 



" But with the gun that is to be tested on the 'Destroyer' we 

 can make a projectile penetrate any of the nettings that are now 

 in use. We are to use a sixteen-inch gun. That which we will 

 experiment with is being constructed at Bethlehem, Penn., and 

 is about half done. It is to be 35 feet in length. The projectile 

 is to be 25 feet long, and to throw it a charge of twenty -five 



