TRANSACTIONS OF SOCIETIES. 1 29 



The reasons of this were discussed and suggestions made for lowering the 

 cost of explosives per ton of reef broken. — " The effect of charcoal in gold- 

 bearing cyanide solutions, with reference to the precipitation of gold " : M. 

 Green. It was found that equal weights of tinely crushed wood charcoal, 

 agitated with gold-bearing cyanide solutions of equal strength, for lengths 

 of time varying from three to 18 hours, in each case precipitated identical 

 quantities of gold, it was also found that freshly-ignited wood charcoal 

 precipitated 90 per cent, of the gold contained in a stock cyanide solution, 

 while similar charcoal, after six months" exposure, precipitated only 50 

 per cent. ; also that sugar charcoal obtained by heating sugar in closed 

 retorts precipitated 62 per cent, of the gold, sugar charcoal prepared by 

 treatment with sulphuric acid failed to precipitate any gold whatever. Dis- 

 cussing the underlying principles of the effect of charcoal in cyaniding, the 

 author concluded that charcoal does not stop the passage of a dissolved 

 substance through it by means of an osmotic effect, but that its power as a 

 precipitant of gold from aurocyanide solution is due to occluded gases, 

 loosely held gases having little or no influence. It appears to be mainly 

 carbon monoxide that is responsible for the power of charcoal thus to preci- 

 pitate gold. 



South African Society of Civil Enginfeks. — Wednesday, September 

 loth : A. D. Tudhope, M,.I.C.E^, Vice-President, in the chair. — "The water 

 supply of Kingwilliamstown " : T. G. Caink The water is obtained from 

 a catchment area of about 9„300 acres, consisting of forest-clad mountains 

 rising to between 3,000 and 4,000 feet above the dam. Rain gauges near 

 the top and bottom of the catchment area show T6-year averages of 

 respectively 74 and 2>7 inches of rain per annum. The water shows a 

 remarkable absence of silt, even after severe storms, and has no trace of 

 the brown colour characteristic of Western Province rivers. The run-off 

 from the catchment area amounted to 4,968 million gallons in 1911 and 

 1,980 million gallons in 1912. The dam is curvilinear on the middle portion,, 

 with a straight length on either side. Detailed descriptions of the con- 

 struction of the dam, reservoir and pipe line were given by the author. 

 The water, on reaching- the town, passes through " Candy '' filters, and the 

 monthly consumption during 19 12, by a population sliglitly over 9,0.00. of 

 whom about 3.400 are natives, averaged close on thirteen million gallons. — 

 '■ X()tes on the casting and driving of reinforced concrete piles " : H. A. 

 Fuhr. A description of the operations involved in the construction of tlie 

 Tyumie River Bridge, Alice, Victoria East, Cape. 



Wednesday, October 8th: G. T. Nicholson, AI.I.C.E., Vice-President, in 

 the chair. — " The Stockton tunnel " : A. Colman. The tunnel is on the 

 Natal main line, between Mooi River and E^tcourt, and constitutes a 

 deviation whereby the high watershed, previously crossed by a deep open 

 cutting at an altitude of 5,300 feet, is reduced in elevation to 4,980 feet, 

 and the ruling gradients of i in 30 have been eased to i in 65, at a cost of 

 half a mile of tunnel and a deviation two miles to the west. 



South African Institution of" Engineers. — Saturday, October nth: 

 ]\Ir. W. Calder, President, in the chair. — "Air consumption and mainte- 

 nance costs of rock drills": E. G. Izod, and E. J. Laschinger. 

 Greater economy in the use of compressed air for transmission of power 

 w-as urged. Air power is mainly used for actuating rock-drills, and on 

 an average twice as much compressed air is used on a development shift 

 as on a stoping shift. That large savings in the air-power bill of the 

 mines may be eft'ected is shown by the fact that in one group of mines, a 

 saving of over one shilling per machine shift in the air power cost as 

 lietween January and December, 1912, was l)rought about; in other words, 

 there had been a saving of 1.205.038 air units, notwithstanding an increase 

 in the number of rock-drill shifts during the same period from 73,926 to 

 78,545. With regard to maintenance, there had been a saving comparing 

 January witli Decemi)er, of 51 shillings on every 52 machine shifts worked. 

 Suggestion"^ were made as to the lines along which such savings might be 

 effected. 



