392 



NATURE 



{Sept. 10, 1874 



engine or train having quitted it ; and is sufficiently presumed 

 not to have met with any other obstruction, by shunting of 

 carriages or waggons, or by accident, or in any other way. 



This new arrangement, which appears to be a very important 

 improvement, has already been brought into action with success 

 on several sections of tlie Caledonian Railway ; and it is being 

 exrended as rapidly as possible on the lines of the Caledonian 

 Com]3any, where the ordinary mode of worlcing the block system 

 has hitherto been adopted. 



The mechanisms and atrargements I have now briefly men- 

 tioned are only a portion of the numerous contrivances in use 

 for abatement of danger in railway traffic. It is to be under- 

 stood that by no mechanisms whatever can perfect immunity 

 from accidents be expected. The mechanisms are liable to 

 break or to go wrong. They must be worked by men, and the 

 men are liable to make mistakes or failures. We shall con- 

 tinue to have accidents ; but, if we cannot do away with every 

 danger, that is no reason why we should not abate as many 

 dangers as we can. 



Within the past twenty years very remarkable progress has 

 been made in steam navigation generally, and more especially, 

 I would say, in oceanic steam navigation. In this we meet 

 with the realisation of great practical results from the com- 

 bination of improved mechanical appliances, and of physical 

 processes depending on a more advanced knowledge of thermo- 

 dynamic science. 



The progress in oceanic steam navigation is due mainly to the 

 introduction jointly of the screw propeller, the compound engine, 

 steam jacketing of the cylinders, superheated steam, and the 

 surface-condenser. 



The screw propeller, in its original struggle for existence, 

 when it came into competition with its more fully developed 

 rival, the paddle-wheel, met with favouring circumstances in 

 the want then strongly felt of means suitable for giving a small 

 auxiliary steam-power to ships arranged for being chiefly pro- 

 pelled by sails. For the accomplishment of this end the paddle- 

 wheel was ill suited ; and so the screw propeller got a good 

 beginning for use on long oceanic voyages. Afterwards, in the 

 course of years, there followed a long series of new inventions 

 and improved designs in the adaptation of the steam-engine for 

 working advantageously with the new propeller ; and it has re- 

 sulted that now, rnstead of the scr-ew being used as an auxiliary 

 to the sails, the sails are more commonly provided as auxiliaries 

 to the screw. For long oceanic voyages it became very impor- 

 tant or essential to get better economy in the consumption of 

 fuel. In order to economise fuel, high-pressure steam, with a 

 high degree of expansion and with condensation, was neces- 

 sary. This led, to the practical adaptation for the propulsion of 

 vessels of the compound engine, an old invention which origi- 

 nated with Hornblower in the laiter part of the last century, and 

 was afterwards further developed by WollT. The high degrees 

 of expansion could not be advantageously used in cylinders 

 heated only by the ordinary supply of steam admitted to them 

 for driving the piston ; and more especially when that steam 

 was boiled off directly from water without the inti'oduction of 

 additional heat to it after its evaporation. The knowledge of 

 this, whicli was derived through important advances made in 

 thermo-dynamic science, led to the introduction into ordinary use 

 n steam navigation of steam-jacketed cylinder's, and to the 

 ordinary use also of superheated steam. With increased efforts 

 towards economy of space in the liold of the ship, which 

 became the more essential when very long voyages were to be 

 undertaken, and with the new requirement of greatly increased 

 pressure in the steam, the old marine boilers, witli their flues 

 of riveted plates, were superseded by tubular boilers more 

 compact in their dimensions and better adapted for resisting 

 the high pressure of the steam. In connection with the>e 

 various changes the old difficulty of the growth of stony incrus- 

 tations in the boilers became aggravated rather than in any 

 way diminished. As the only available remedy for this, there 

 ensued the practical development and the very general intro- 

 duction of the previously known but scarcely at all used 

 principle of surface condensation instead of condensation by 

 injection. A supply of distilled water from the condenser is thus 

 maintained for feeding the boilers, and incrustations are avoided. 

 The consumption of coal is often found now to be reduced to 

 about 2 lbs. per indicated liorse-power per hour, from having 

 been 4 or 5 lbs. in good engines in times previous to about twenty 

 years ago. 



beio.e the times of ocean telegraph cables, very little had been 

 done in deep-sea sounding ; but when the laying of ocean cables 



came first to be contemplated, and when it came afterwards to 

 be realised, the obtaining of numerous soundings became a 

 matter of essential practical importance. In the ordinary 

 practice of deep-sea sounding, as carried on, both belore and 

 since the times of ocean telegraph cables, until a year or two 

 ago, a hempen rope or cord was used as the sounding line, and 

 a very heavy sinker, usually weighing from two to four hundred- 

 weight, was required to draw down the hempen line with 

 sufficient speed, because the friclional resistance of the water 

 to that large and rough line moving at any suitable speed was 

 very great. The sinker could not be brought up again from 

 great depths ; and arrangements were provided, by means of a 

 kind of trigger apparatus, so that when the bottom was reached 

 the sinker was detached from the line and was left lying lost 

 on the bottom ; the line being drawn up without the sinker, 

 but with only a tube, of no great weight, adapted for receiving 

 and carrying away a specimen of the bottom. For the operation 

 of drawing up the hempen line with this tube attached, steam 

 power has been ordinarily used, and practically must be regarded 

 as necessary. 



A great impr-ovement has within the last two or three years 

 been devised and practically developed by Sir William Thomson. 

 Instead of using a hempen sounding line, or a cord of any kind, 

 he uses a single steel wire of the kind manufactured as pianoforte 

 wire. He has devised a new machine for letting down into the 

 sea the wire with its sinker, and for bringing both the wire and 

 the sinker up again when the bottom has been reached. With 

 his apparatus, in its earliest arrangement and before it had 

 arrived at its present advanced condition of improvement, he 

 sounded, in June 1872, in the Bay of Biscay, in a deptli of 

 2,700 fathoms, or a little more than three miles, and brought up 

 again his sinker of 30 lbs. weight, after it had touched the 

 bottom ; and brought up also an abundant specimen of ooze from 

 the bottom, in a suitably arranged tube attached at the lower end 

 of the sinker. 



An important feature in his machine consists in a friction- 

 brake arrangement, by which an exactly adjusted resistance 

 can be applied to the drum or pulley whiclr liolds the wire 

 coiled round its circumference, and which, on being allowed to 

 revolve, lets the wire run off it down into the sea. The resist- 

 ance is adjusted so as to be always less than enough to bear up 

 the weight of the lead or iron sinker, together with the weight 

 of the suspending wire, and more than enough to bear up the 

 weight of the wire alone. Thus it results that the arrival of the 

 sinker at the bottom is indicated very exactly on board the ship 

 by the sudden cessation of the revolving motion of the drum 

 from which the wire was unrolling. 



Another novel feature of great importance consists in the in- 

 troduction of an additional hauling-up drum or pulley arranged 

 to act as an auxiliary to the main drum during the hauling-up 

 process. The auxiliary drum has the wire passed once or twice 

 round its circumference at the time of hauling up, and is 

 turned by men so as to give to the wire extending from it into 

 the sea most of the pull requisite for drawing it up out of the 

 sea, and it passes the wire forward to the main drum, there to 

 be rolled in coils, relieved from the severe pull of the wire ami 

 sinker hanging in the water. Thus the main drum is saved 

 from being crushed or crumpled by the excessive inward pres- 

 sure which would result from two or three thousand coils of very 

 tight vvSre, if that drum unaided were required to do the whole 

 work of hauling up the wire and sinker. 



The wire, though exposed to the sea-water, is preserved against 

 rust by being ke] t constantly, when out of use, either immersed 

 in or moistened with caustic soda. The fact that steel and iron 

 may be preserved from rust by alkali is well known to chemists, 

 and is considered to result from the effect of the alkali in neutral- 

 ising the carbonic acid contained in the water, as the carbonic 

 acid appears to be the chief cause of the rusting of steel and 

 iron. 



This new meihod of sounding, depending on the use of piano- 

 forte wire, was first publicly explained by Sir Wiljiam Thomson 

 in the Mechanical Section of the Bridsh Association at the 

 Brighton meetrng two years ago ; and in the interval whicli 

 has since elapsed, it has come rapidly into important practical 

 use. 



I have to-day already brought under your notice a system 

 of elaborately contrived and extensively practised methods of 

 signalling and otlrerwise arranging for the safety of trains in 

 motion on railways These melliods, m the agj^regate, as we 

 have them at present, may be lonked on as the result of a 

 gradual development, which, through design and intelligent 



