508 REPORT—1905. 
maintain a stable condition of combustion under all variations cf fuel supply, &e. 
tozether with the belief that, could such a thing be found, the beautiful perfection 
of this method of burning coal would eventually overcome all the remaining 
difficulties in the way of its practical application, which led the writer on through 
the experiments that he then described. 
It was at this time that a correct idea was obtained of the principles governing 
the combustion of explosive mixtures in motion, and it became clear that means 
must be provided for heating the incoming mixture in some other manner than by 
radiation from the brickwork alone. It was recognised that what was required 
was a source of heat which would have a natural and strong tendency to travel 
parallel and in a contrary direction to the incoming combustible. 
When considering the economical aspect of the question it is to be remembered 
that money must be expended to make coal-dust, and that this amount is to be 
added to the original cost of the coal for dust-firing when comparisons are 
made, 
It will be of interest to see what percentage improvement is necessary over 
present boiler practice on the Rand to make dust-firing a commercial success. 
For this purpose it will be assumed that the boiler plant will be large enough to 
consume ninety tons of coal per day of twenty-four hours, and that ample 
spare machinery be provided. ‘The cost per annum would then be :— 
£ 
Interest and redemption . : ; - . .- 402 
Repairs and maintenance : : : ; - 550 
Sundry stores . : . : : : = . 300 
Power = F 5 5 5 : : ; . 2,970 
4,222 
Deduct labour saved . - ‘ ‘ . 1,034 
£3,188 
This amount divided by the yearly tonnage, viz., 32,850 tons, makes the cost 
per ton Is. 113d. As the average cost of coal to the majority of mines on the 
Rand is about 12s., it will be seen that an average saving of 16 per cent. must be 
shown. . 
On referring to the tabulated statement of the tests it will be seen that with 
dust-firing 7:8 lbs. of water were evaporated from and at 212° F. per Ib, of coal, 
and with hand-firing 5:5 Ibs. were evaporated; or, in other words, 29 per cent. of the 
coal was saved, This figure when compared with the limiting one of 16 per cent. 
shows that, even with the means now at our disposal, when compared with poor 
hand-firing, dust-firing is commercially possible. 
FRIDAY, SEPTEMBER 1. 
The following Papers were read :— 
1. The Harbours of South Africa, with special reference to the Causes ana 
Treatment of Sandbars. 
By Catucart W. Meruven, /.24.8.2., MInst.C.H. 
The author gave a short description of the littoral of South Africa from Cape 
Town to Delagoa Bay, referring to the remarkable absence of deep-water indenta- 
tions forming natural harbours between these points, and gave some of the reasons 
therefor. The description included some of the most notable features of the 
southern and eastern coast lines of Cape Colony and Natal, including Zululand. 
Reference was also made to the formation of some of the lakes and lagoons and 
the gradual elevation of the coast belt as affecting these. 
