182 



SUGAE. 



and uniformity of temperature are necessary. As they have to 

 remain crystallizing from three months to six months, a large pro- 

 vision of tanks is required. These seem to answer best when built 

 of masonry and plastered with native cement. The third boilings 

 form about 1^ per cent, of the raw juice ; hence, in a factory work- 

 ing ninety days, at the rate of 6000 gallons an hour, tanks to 

 accommodate 194,400 gallons would be required. The total horse- 

 power required to work the Aba factory, assuming that a cubic foot 

 of water at 62° Fahrenheit evaporated at 212° represents a horse- 

 power of boiler duty, is computed as follows : 



The four cane-mill engines take 68 I.H.P. each. Allowing h.p. 



25 lbs. of steam per H.P. per hour, which will cover loss by 



steam pipes, &c., they w ill require of boiler power 112*0 



The clarifiers have to heat 6000 gallons of juice per hour, from 



72° to 212° and to boil for five minutes, and will absorb ,. 163-5 

 The concentrators having to raise 5473 gallons of juice from 



160° to 280°, and to evaporate 3118 gallons under 3 lbs. 



pressure, will take 519 '0 



Steam under 60 lbs. pressure used in steaming centrifugals, 



calculated 11*2 



Sulphurous acid pumps, calculated 1*5 



Donkey feed-pumps „ 2*3 



Total H.P. = cubic feet of water to evaporate from 62° Fahr. = 809 • 5 



or nearly 11 H.P. per ton of sugar per 24 hours. If 8 lbs. of coal 



are necessary to evaporate a cubic foot of water from 62° then 

 6476 lbs. of coal would be necessary to produce 6744 lbs. of sugar, 

 or the weight of coal will be 96 per cent, of that of the produce 

 in sugars. Supposing the cane mills to express 68 per cent, of juice, 

 the 6000 gallons per hour would produce 30,325 lbs. of wet megass. 

 From experiments made on a large scale by Mr. Black, the resident 

 engineer of the Magaga sugar factory, it appears that dry megass, 

 fit for burning, weighs 53 per cent, of the wet ; and he found that 

 29,578 lbs. of dry megass did as much as 16,000 lbs. of ordinary 

 north country coal, or that it required 1*85 lb. of megass to do the 

 same work as 1 lb. of coal. The canes yielding 6000 gallons of 

 juice, therefore, produced 16,072 lbs. of dry megass, which, consumed 

 in the evaporation of 809 * 5 cubic feet of water, gives nearly 20 lbs. 

 of megass to the cubic foot. According to Mr. Black, 14*8 lbs. 

 should be enough ; but an imperfect experiment, made on a small 

 Cornish boiler at Magaga, gave only 3*06 lbs. of water per 1 lb. 

 of megass, or 20*7 lbs. to the cubic foot. As an approximation, 

 Mr. Black considers that 1 lb. of coal is equal to 2 lbs. of megass, 

 or 16 lbs. of megass to the cubic foot of water, so that there seems 

 to be margin enough to warrant the statement, that the refuse of the 

 canes should give fuel enough to make the sugar ; and this would 

 especially be the case in Egypt, where the climate is favourable to 

 drying the megass. 



" In addition to the megass, most of the Egyptian mills are said to 

 consume one ton of coal per ton of sugar, but the true statistics are 

 difficult to arrive at. I believe that in some of the factories in the 



