June 1, 1897.] 



KNOWLEDGE. 



133 



It was only in 1888 that a steamship, the Great 

 Western, of about two thousand tons displacement, com- 

 menced a regular service between Bristol and New York, 

 making the passage across the Atlantic in about fourteen 

 days. The advance in the adoption of steam propulsion 

 was so rapid that in 1840 steamers were regularly running 

 to India. Now, eighty-eight per cent, of our ocean traffic 

 is carried on by steamers, and a vessel has recently been 

 launched at I3elfast having a displacement of no less 

 than thirty thousand tons ; as regards speed, the 

 Turbinia torpedo-boat has recently maintained, on trial, 

 a speed of thirty-two and a half knots (about thirty-seven 

 and a half statute mUes) per hour ; whilst over twenty 

 thousand horse-power for one passenger steamer, with a 

 speed of twenty knots, are not uncommon. Leaving out 

 of account ships of war, the commercial fleet of the United 

 Kingdom and its dependencies in 1837 was represented by 

 about two million five hundred thousand tons, of which 

 only about one hundred thousand tons were steamships, 

 and most of these used steam as auxiliary to sails. Now 

 the registered tonnage of our commercial navy extends to 

 ten million five hundred thousand tons, of which steam 

 vessels are to sailing ships in the ratio of about two and 

 a half to one, and the latter are rapidly disappearing. It 

 is said that in the forthcoming Jubilee naval review, off 

 Spithead, spectators will see, probably for the last time, 

 warships with masts and yards taking part in a naval 

 display. 



During the interval referred to, the total of our exports 

 and imports has risen from one hundred and forty million 

 to seven hundred million tons. In 1810 our ships took 

 twenty-seven per cent, of the world's carrying trade ; now 

 they take fifty-two per cent., or, including colonial ships, 

 sixty per cent. 



To keep pace with the enormous increase In our marine 

 carriage, shipbuilding has advanced by leaps and bounds. 

 This is shown by the following table, giving approximately 

 the figures for ships of all kinds built in the United 

 Kingdom during 1896 : — 



Phi 



wliere Tesae's were built. 



Clyde 



Tyne 



Wear 



Tees 



Belfast 



Other Ports (including the Dockyards) 



Total 



G-ross Tonnage. 



421,000 

 246,800 

 218,400 

 118,400 

 119,600 

 272,000 



1,891,200 



These figures show clearly the immense importance of 

 this, which may be called the only exclusively British 

 industry, the figures for any other country being com- 

 paratively insignificant ; but the United States is rapidly 

 improving its position in this regard. 



Probably no discoveries have had so great an effect in 

 rendering possible the foregoing advances in railway and 

 marine engineering as the introduction of the Bessemer 

 process of making steel, in 1856, and of the modern 

 Siemens-Martin method. Formerly, wrought-iron rails 

 cost about thirteen pounds per ton ; now steel rails of 

 excellent quality can be bought at three pounds fifteen 

 shillings per ton. To Bessemer is due in a great measure 

 the credit of the advance in steel making, though the 

 open-hearth process is now rapidly taking the first place. 



The excellent qualities of many recently discovered 

 bronzes and alloys have enabled the modern mechanical 

 engineer to make great advances Ln regard to the strength 

 of special details, with a great reduction in friction. 



CIVIL ENGINEERING WORKS. 



The increase in railway enterprise has necessitated the 

 construction of bridges and tunnels of great magnitude. 

 Of these the Forth Bridge in Scotland, the Brooklyn 

 Bridge in America, and the Tower Bridge in London, 

 are among the most remarkable, whilst the St. Gothard 

 and Severn Tunnels are among the greatest. 



It is only necessary to remind the reader that the Forth 

 Bridge has spans of one thousand seven hundred feet, 

 bridged by two cantilevers, each six hundred and seventy- 

 five feet long, with a central girder three hundred and fifty 

 feet long, the cantilevers being three hundred and fifty 

 feet deep at the piers and fifty feet at the centre, with a 

 height of three hundred and fifty-four feet above the water, 

 the length of the bridge being over a mile. The contract 

 was let for one million six hundred thousand pounds, but 

 the total cost considerably exceeded this. The Brooklyn 

 Suspension Bridge has a clear span in the centre of one 

 thousand five hundred and ninety-five feet, the height 

 above high water being one hundred and thirty-five feet. 

 The cost was estimated at about three mOlion pounds. 

 The St. Gothard Tunnel is fourteen thousand nine hundred 

 and twelve metres (about nine and a quarter miles) long, 

 whilst the Severn Tunnel has a total length of about four 

 and a half miles, of which two and a quarter miles are under 

 the tideway of the estuary of the Severn. The Black wall 

 Tunnel, under the Thames, just opened, with a length of 

 over a mile, constructed at a cost of over one million 

 pounds, is worthy of mention. 



Tiie Tower Bridge is, perhaps, the most beautiful work 

 of the kind in existence. The method of opening the 

 bridge to river trafiic by the rotation of the bascule leaves 

 or spans — each one hundred and sixty-three feet long, fifty 

 feet wide, and weighing one thousand two hundred tons, 

 about great pivots one foot nine inches in diameter resting 

 on roller beirings — is so well known as to require no 

 detailei description here. The cost of the bridge was 

 about a million pounds sterling exclusive of the cost of 

 land. The average time during which the road traffic is 

 interrupted by the opening of the bascules is only about six 

 minutes, and in many cases three minutes suffices. About 

 eight thousand vehicles and sixty thousand pedestrians 

 cross the bridge per day. 



PROGRESS IN MECHANICAL ENGINEERING. 



The perfecting of the steam-engine by the use of higher 

 pressures and triple or quadruple expansion, which, with 

 other improvements, has reduced the amount of coal 

 required per horse-power per hour to about one and a half 

 pounds, and the introduction of the steam turbine, are the 

 main features in steam power generation. The gas-engine, 

 and more recently the oil or petroleum engine, have 

 developed with great rapidity. Both the latter may be 

 said to have appeared during the Queen's reign. It is true 

 that Barber, Street, Lebon, and others, towards the end of 

 the previous century, had done something in this field, but 

 the first commercially successful gas-engine was the 

 " Lenoir " of 1860. The great advantages of the gas or 

 oil engine are the facts that it requires no boiler ; that it 

 can be started or stopped when required ; that, as a rule, 

 skilled attendance is not required ; and that it occupies 

 comparatively little space for the power developed. Also 

 a good efficiency is possible, i.e., a large power can be 

 obtained from a small weight of fuel ; but in the case of the 

 gas-engine it must be remembered that this fuel has 

 usually to be obtained from the mains of a gas company, 

 and is therefore expensive. The oil-engine has been 

 developed mainly since 1872, and is now rapidly taking the 

 lead as a useful, efficient, and convenient motor. 



The use of this motor for the propulsion of road carriages 



