TRANSACTIONS OF SECTION G. 805 



an addition to the present English stock, and worked in combination with the 

 present couplings and buffers. 



3. Hydraulic Attachment to Sugar Mills} By Duncan Stewart. 



The object of this paper was to explain the application of hydraulic pressure to 

 the rollers of sugar-cane crushing mills and their connection with a loaded accu- 

 mulator giving the power to the planter or his manager to regulate the crushing of 

 the canes to a pressure which will be known to him or them. In this arrangen^nt 

 the percentage of juice can be extracted equal on all the canes passing through the 

 mill, whether the feeding be regular or not. 



It will also act as a safety-valve on the working of the engine, gearing, and mill, 

 and will not only allow the engineer to proportion the various parts of the plant to 

 certain strains, but to scheme mechanical arrangements for feeding the mill which 

 have hitherto been done by manual labour. 



It will crush with such regularity that the megass may be used as fuel at once. 

 The saving in money, besides the freedom from liability to breakage, has been 

 reckoned at 20s. per ton of sugar made, and it is now at work in more than fifty 

 sugar estates and factories. 



4. Forced Draught. By J. R. Fotheegill. 



Forced draught, or mechanically supplying air above atmospheric pressure to 

 the furnaces of steam boilers, has been the subject of many patents during the last 

 fifty_ years, but it is only within the last two or three years, particularly in its 

 application to merchant steamers, that practical success has been achieved. 



The writer views the 'closed ash-pit' system as the best for merchant 

 steamers. 



After reviewing the chemical composition of average British steam coal and the 

 oxygen required for the chemical combustion of its consumable constituents, the wi-iter 

 gave the quantity of air required at 62° Fahr. for 1 lb. of coal as follows : — 



For the volatilised gases 50 cubic feet. 



For the fixed carbon 90 



or a total of 140 cubic feet, equal to 10-7 lbs. 



In actual practice 22 to 24 lbs. of air are required, but with forced draught 

 judiciously applied 16 to 18 lbs. prove sufficient ; therefore the reduction of furnace 

 temperature and loss of heat carried away by the use of 24 lbs. of air are avoided 

 and a saving effected in proportion. 



By the use of forced draught we are enabled to regidate the distribution of the 

 ■air at will andby supplying the requisite quantities to the gases and fixed carbon 

 we readily bring about the chemical union of tl:e oxygen vfith the carbon to 

 produce carbonic acid, giving 14,500 heat units, instead of only 4,400 by the 

 formation of carbonic oxide. 



The writer then proceeded to show in what manner and how the air supply should 

 take place, pointing out the defects and difficulties in the regulation and distribution 

 of air to the furnace under the ordinary conditions of natural draught. 



In September 1884 the writer applied forced draught to the boiler of the s.s. 

 Marmora, which steamer ran eleven consecutive voyages of sixteen days' steaming per 

 -voyage before she was wrecked, with a saving per voyage of 33/. 16s. 7d., equal to 

 43 per cent, in the cost of the bunker coals, as compared with eleven voyages prior 

 -to the alteration. 



Drawings in plan and section illustrating the arrangement fitted to the Marmora 

 were shown and a general description given of the arrangement, indicating par- 

 ticulars as to the air admission and distribution, water-gauge pressure, grate area, 

 .and the necessitj'- of a damper in the funnel, &c. 



Utilising the heat of the waste gases to increase the temperature of the air 



' Published in extenso in The Sugar Cane, Dec. 18S6. 



