'^— 



TRAXSACTIOXS OF SOCIliTIKS. 28/ 



account was gi\tn dt the v.irinus surveys undertaken in order in improve 

 the Natal ^[ain Line between Pietennaritzlnirg and Riet Spruit, and of 

 the main economic features of tlie deviation eventually decided on. and 

 now under construction. — " XoIl's en the rL-coiistntctioii of railz<.'i.iy. Li'idcr- 

 itzbucht to Ji'iiidltiik : W. G. Cocks. Tlie wliole distance from Liideritz- 

 bucln to Windinik'. in (ierman South-West Africa, is approximately 540 

 miles. A general description of the line was given, followed hy an outline 

 of the reconstruction work. The plate-laying was carried out by a day 

 and a night gang, each comprising some 150 natives, under control of a 

 railway engineer officer, and accompanied by the necessary complement 

 of sapper plate-layers. Ahead of tliese gangs was a permanent fatigue 

 part.\ 'if rco Kattrarian Riiies. clearing b:dlasi. getting sole plates ready 

 for the reception of rails, etc. In advance of these was a rail-cutting 

 party of 160 natives. Examples were given of the nature of the work 

 done hy these: thus, l)etween jnd April and 17th [May. a section of the line 

 76 miles in length, whereof ever\ rail had been destroyed, was recon- 

 structed and opened for traffic. The total number of rail cuts was 49.5j6. 

 With regard to bridges, 42. principally plate girder and truss types, which 

 had been destroyed, were repaired, bird-caged, and trestled. At the 

 watering staions, 21 in number, the pump heads had been destroyed in 

 nearly every case, the boreholes plugged with debris, and all the wells 

 had been poisoned. A section of the Engineer Corps was detailed to 

 obtain water and repair the boreholes ahead of the constructi<jn train, and 

 so there was generally sufficient water available to work the train 

 forward. 



South Africax Institute of Electrical Exgixei'.ks. — Thursday, 

 September i6th : B. Price. Al.I.E.E.. President, in the chair. — ■" Xotcs on 

 three-phase tniiisfoniiers'' : A. X. Aikman. The points di.-^cussed with 

 more or less detail included temperature rise, overload capaeitx. sludging 

 of oils, parallel running of transformers, etc. 



Thursday, October 21st: B. Price, :\I.T.E.E.. President, in the chair.— 

 " Some notes on the coniparatk'C costs of compressed air and electricity 

 for use in mine stope haulages": A. E. Middleton. The foUowhig 

 comparative conditions were shortly discussed : ( i ) relative consumption 

 of air and electricity, corrected for transmission and transformation losses. 

 (2) relative maintenance costs, (3) relative tirst costs. The author arrived 

 at the conclusion that the air winch costs live or six times more for power 

 to rmi than the electric. In regard to repairs and maintenance, the total 

 monthly cost for an air winch was estimated at £3 15s. 8d.. and for an 

 electric winch £2 i8s. 6d. On the other hand, the heavy cost of cables for 

 electrically-driven winches is the chief adverse factor against their adop- 

 tion. 



Thursday, November i8th • Prof. W. Buchanan, M.I.E.l-^. \'ice- 

 President, in the chair. — "Tlie distribution plant of the Jo' auiiesburti 

 Municipal Electric supply system": Prof. J. H. Dobson. A compre- 

 hensive description of the various distribution systems was given under 

 the following heads: (i) the '"inner" or town area, (2) the "outer" 01 

 suburban area, (3) the power .-supply to the tramways, (4) public street 

 hghting. The author concluded by comparing the system as it was in 1909 

 with its dimensions in 1914. During this period the connections to the 

 mains increased from 5.720 to 16,091, and the total units consumed from 

 Ti millions to 25 millions. The number of consumers connected to the 

 Johannesburg electric distribution system is approximately equal to 

 those on the whole of the other municipal undertakings in South Africa. 



Tuesday, December 21st : B. Price, M J.E.E.. President, in the chair. — 

 "A power factor diagram": C. J. Constancon. The author exhibited 

 and described a diagram from which the power factor of a circuit can be 

 found immediately, without anv calculation from the two wattmeter read- 

 ings of a three-phase system. The readings of the two wattmeters are 

 looked up on the orthogonal axes of the diagram, and then, by following 

 up certain lines on the diagram, the resulting power factor is read ofT on 

 a clearly-iTiarked scale. 



