664 



NA TURE 



[October 31, ^907 



Matiretania by torsion meters directly applied to each 

 shaft. Two wheels are fitted on tlie shaft at some 

 distance apart, each of which in its rotation makes an 

 electrical contact. The contacts are exactly in line, 

 and therefore are coincident in point of time when 

 the shaft is at rest. When the shaft is rotated it 

 suffers torsion, and the aft contact lafjs behind the 

 forward one. The angle of the lag measures the tor- 

 sion. The instrument is calibrated bv determinations 

 made in the shops of the twist which the shaft suffers 

 from couples of known magnitude. In the navigat- 

 ing house of the Matiretania are four dials, on each 

 of which a hand revolves in the direction and at 

 the speed of the particular propeller shaft to which 

 it is attached. It is obvious that the torsion meter 

 might be so adjusted as to give direct records on the 

 bridge of the work of each turbine from moment to 

 moment. 



The two most impressive parts of the machinery 

 are the controlling platform, already mentioned, of 

 the engine-room, where a few small levers control 

 the gigantic forces pent up in the long polished 

 barrels of the turbines, and the small, easily manipu- 

 lated wheel in the wheel-house, which, bv means of 

 a small hydraulic motor, controls the enormous steer- 

 ing engine sunk below water level some 650 feet 

 distant ! 



The plates of the Mauretania were delivered rolled 

 to a guaranteed thickness. This is, I believe, a new 

 departure in the building of English merchant ships, 

 and it enabled the builders to save 500 tons of dead 

 weight. The use of silicon steel in the boilers effected 

 a further saving of 500 tons, making a total of 1000 

 tons, which, reckoned as cargo, represent a gain to the 

 Cunard Company of about 22,oooZ. a year in the earn- 

 ing power of the vessel. An interesting saving in dead 

 weight was also effected in connection with the decora- 

 tion. The lifts in the well of the main staircase are 

 enclosed by a beautiful piece of metal work adapted 

 from existing sixteenth-century wrought-iron work. 

 It is carried out in aluminium instead of iron, and 

 thereby 20 tons weight is saved. One wonders 

 whether the high affinity of the metal for chlorine 

 and the presence of chlorides in sea air have been 

 adequately taken into account. 



The engine-room of the Mauretania, despite the 

 absence of the main reciprocating engines, is very 

 closely packed, and the greatest ingenuity is mani- 

 fested in the arrangements. The four main turbines, 

 each of 15,000 h.p., are controlled from a tiny plat- 

 form by six small levers. Over the great engine- 

 room steam pipes arch large enough for a boy to walk 

 through, and the exhaust from each low-pressure tur- 

 bine passes through a " pipe " 14 feet bv 16 feet ! 

 The distinctive noise of the engine-room is the con- 

 tinuous roar of the steam passing through the main 

 steam pipes. The engine-room, counting main tur- 

 bines, turbo-generators, and auxiliary engines, holds 

 machinery capable of developing something over 

 So, 000 h.p., and the rotating mass of the main tur- 

 bines amounts to about 600 tons, and rotates about 

 200 times a minute. 



The gigantic low-pressure turbines receive the 

 steam at nearly atmospheric pressure, which falls to 

 a condenser pressure of about minus 27 inches of 

 mercury. Ingenious gauges are fitted on each tur- 

 bine, which record the pressure at different steps in 

 the expansion, so that, should some of the blades 

 become stripped, the injury can be at once located. 



The stokeholds are so efficiently ventilated bv 

 powerful fans as to be cool save when the furnace 

 doors are actually opened, in spite of the presence 

 of 192 furnaces. 



NO. 1983, VOL. 76] 



The magnitude of the strains which a ship 

 nearly the length of the Houses of Parliament 

 must experience in a heavy head sea is brought to 

 mind by the provision whicli has been made for bend- 

 ing. The boat deck, together with the deck houses 

 on it, which contain the long suite of public rooms, 

 are cut completely through in three places, so as to 

 allow the ship to give longitudinally. 



No description can give the effect of the stately 

 progress of so great a ship down the narrow Tyne. 

 The grey autumn day, the cheering crowds piled on 

 the hill-sides to their summits, and the anxious pilot 

 striving to make his orders heard amid the clamour 

 of steam whistles and fog signals, are vivid recollec- 

 tions. So, too, are the raucous blasts of welcome flung 

 to us from the great headlands as we passed them 

 by. The sombre cliffs of the Pentlands in the grey 

 dawn. Cape Wrath under the autumn sun, lonely 

 light vessels, tiny fishing craft, and liners, each after 

 its own fashion wished us the freedom of the seas. 



W. B. H.XRDY. 



THE GEOLOGICAL SUCCESSION IN SOUTH 

 AFRICA.' 



EVERY year our l^nowledge of the geological suc- 

 cession in South Africa becomes more extended 

 as a result of the labours of the Geological Commis- 

 sion of the Cape, the Geological Survey of the Trans- 

 vaal, and the host of private workers who contribute 

 to the Transactions of the Geological .Society of South 

 Africa. The newly published Report of the Cape Com- 

 mission for the year 1906. and the Transactions of the 

 Geological Society for the period January to June of 

 this year, are full of interesting matter. The Cape 

 surveyors have been worlving in Bechuanaland and 

 Griqualand West, and have thus come into close 

 contact with the work of the Transvaal geologists ; for 

 although the operations of the official Survey of the 

 Transvaal have as yet been confined to the Pretoria 

 and Middelburg districts, the Marico district and the 

 neighbourhood of Mafeking have been explored by 

 unofficial geologists in the employ of big land com- 

 panies. Pioneer work of this nature, although un- 

 sanctified bv official publication, is not to be 

 contemned, since in many cases it is done, under condi- 

 tions of considerable difficulty, by enthusiastic geolo- 

 gists and keen observers whose labours have often 

 laid the foundation for the detailed work of the 

 Government surveyors. 



The earliest work in Griqualand West was by Mr. 

 G. W. Stow, who communicated some of his results 

 to the Geological Society of London (O.J.G.S., vol. 

 XXX., pp. 5ST-680, 1S74). Unfortunately, a consider- 

 able proportion of his observations was embodied in 

 reports to the Griqualand West Government, which 

 since they were handed in have never emerged from 

 their pigeon-holes. However, his classification of the 

 Griqualand West rocks has, with the exception of the 

 Keis series, been adopted by the Cape Survey. It is 

 as follows : — 



M.itsap Series Quartzites and conglomerates 



(uncnnfcrmilv) 



f Griqualown Series ... Magnetite-jasper rock": 



-\ Cam|ibe]I Rand Series ... Limestone and quartzite 



V Keis Series Quartzites and mica schists 



I 



1 K)eventh Annual Keport of the r.eolcgical Commission of the Colony 

 of the Cape of Good Hope, iqo6. (Capetown, 1Q07.) 



GeoloKiral Map of the Colony of the Cape of Good Hope. Sheet 3ilvi. 

 (Published by the Geological Commission, 1907.) 



Transactions of the Geoloeieal Society of South Africa. Vol. x., January 

 to June, 1907. Pp. 1-68. (Johannesburg, 1907.) 



