THE EXTRACTION OF THE JUICE BY MILLS 247 



The Actual Performances of Milling Plants. — In studying the actual 

 performances of milling plants, besides the extraction there is required to be 

 known the size and number of the mills, the preparatory appliances used 

 the tonnage of cane, or more exactly of fibre, treated per hour, the quantity of 

 water added and its method of application, and, finally, the composition of 

 the bagasse. As representative of modern practice, there are given below 

 the crop averages for the Hawaiian Islands (1917), Java (1918), Mauritius 

 (191S) — these being the only districts which have 3'et established a system of 

 mutual control with the annual publication of collated results. Of these 

 figures it may be remarked that the sugar percentage in cane is exceptionally 

 low for Hawaii, and exceptionally high for Java [cf. Chapter II.) 



There do not seem to be available any but isolated statements regarding 

 the work done in Cuban mills. Though there are some mills in Cuba which 

 reach extractions of 95°-96°, in the majorit}' capacity is of so much more 

 importance than quaHty of work that over all Cuba the average extraction 

 is probably not more than 90. The \\Titer would estimate the average 

 quantity of added water as about 10 per cent., and of water in bagasse as 

 but little under 50 per cent. 



As regards capacity of the mills, from data collected by the UTiter and 

 obtained from many sources, such as correspondence, the reports of trav- 

 ellers and occasional pubhshed statements, it would appear that in Hawaii 

 a crusher and 12 roller 78-in. x 34-in. mill treats up to 8 tons of fibre per 

 hour, a similar 66-in. train treating up to 5 tons. In Cuba a double crusher 

 and 15 or i8-roller train (84 in. x 36 in.) wiW treat up to 13 tons of fibre 

 per hour. In Java a crusher and 9 roller train (6o-in. x 30-in.) treats 

 4 tons of fibre per hour, and a similar figure is obtained in Mauritius. 



The Development and Conduct of Imbibition. — In 1840, Robinson as a com- 

 munication from unnamed parties in Mauritius, obtained a patent (8731, 

 1840) for a process of imbibition. He claims the use of hot water sprayed on 

 the bagasse from a perforated pipe in special connection with a six-roller mill, 

 also claimed as novel. At ver\- nearty the same time Daubree^* discussed 

 the possibility of increasing the \deld by this means, and at Payen's sug- 

 gestion there was constructed a five-roller mill in which steam enclosed in a 

 hood was allowed to act on the crushed cane. The earliest description of 

 the process in operation is perhaps that due to Wray, and appearing in his 

 " Practical Sugar Planter," 1S4S. He there describes as workmg in Province 

 Wellesley, a three-roller mill, followed by a two-roller unit as the imbibition 

 mill. A little later Bureau also records the exceptional use of imbibition in 

 Louisiana. 



Dry crashing, however, seems to have remained standard practice. In 

 1874 Russel used an imbibition process successfully in Demerara, and con- 

 temporary records show that the scheme was then considered very advanced 

 practice. His patent (4094 of 1874) includes the use of two mills separated 



