MILKY-WAY 



MILL 



195 





higher degree, as does P. rubella, a small North 

 American species. The root of P. poaya, a 

 Brazilian species, with leathery leaves, is an active 

 emetic, ana in a fresh state is employed in liilions 

 fevers. P. tinctoria, a native of Arabia, furnishes 

 a blue dye like indigo. P. venensoa is by the 

 natives of Java dreaded on account of its noxious 

 heavy odour, which they say causes severe head- 

 ache and violent sneezing. Another medicinal 

 plant of the order is Uattany (q. v. ) Root. The 

 bark of the roots of Monniiui pot ystachia and M. 

 salicifolia is used in Peru as a suletitute for soap ; 

 and Miiiiitiii x/iinn.vi, a South African shrub, pro- 

 duces an eatable fruit. 



Milky-way. See GALAXY. 



Mill. This word is now used in a general way 

 as a name for almost all kinds of manufactories, 

 as well as for machines used for grinding ; but in 

 this article we shall describe only a flour-mill. 

 For other mills, see SPINNING, WEAVING, COTTON, 

 FLAX, WOOL, \-c. 



From time immemorial, until quite recent times, 

 wheat has always lieen ground l>etween two stones. 

 At first hand-mills were used such as are so often 

 mentioned in the Bible, and are still met with 

 amongst uncivilised peoples (see QUEEN) ; but the 

 mill subsequently DM*ed through many mechanical 

 developments up to the large merchant mills now 

 found in every civilised country, some of which 

 recently contained upwards of 100 pairs of large 

 millstones. These were made of 'wihr,' a very 

 hard silicate, the best stones coming from the 

 valley of the Seine. The millstones were circular, 

 usually alMMit four feet in diameter, formed of 

 wedge-shaped pieces strongly cemented together, 

 and Ijound by iron hoops. The surfaces were 

 cut into a series of radiating ridges and furrows, 

 by which means the wheat was pushed from the 

 centre to the circumference of the stones, as well as 

 broken Itetween the edges of the ridges. Great 

 care had to lie taken that the surfaces of the 

 two stones were perfectly level and perfectly 

 parallel to each other. Only the unper stone or 

 'runner' revolved, the lower or ' beilstone ' being 

 fixed. The first successful steam Hour-mill was 

 erected in London in 1784. 



Iron rollers in place of millstones were first 

 practically tried at the roller mill in Pest, 

 founded in 1840 by the patriot Count Szechenyi. 

 Tliis new system, called ' the high grinding or 

 gradual reduction roller system,' ultimately spread 

 throughout Hungary, and made Budapest for many 

 ears the greatest flour-milling centre in the world. 

 y 187.~> this system had lieen adopted by the 

 millers of the north-western states of America, and 

 has enabled them to outstrip their teachers : Min- 

 neapolis is now the largest flour-milling centre in 

 the world, and its mills send a great quantity of 

 flour to England. Since 1880 this system has been 

 universally adopted by large mills, and is being 

 gradually IntrodDMd into small mills also. The 

 great advantage of rollers over millstones is found 

 to be that the former avoid the rasping of the out- 

 side of the wheat berry which was inseparable from 

 millstones, and produced a small quantity of very 

 dark powder which necessarily mixed with the flour 

 and greatly deteriorated its colour. 



The following is a description of the different 

 proee~ses which together form the 'high-grinding' 

 or 'gradual reduction' system of flour-milling. 

 (1) The wheat is cleaned or 'smutted,' as it is 

 termed, by means of sifting, winnowing, and 

 Ix-ing put through a cylinder of wire-cloth, with 

 rapidly revolving arms inside, which combines 

 the ai-tions of sifting and polishing the wheat. A 

 machine furnished with hard brushes is often 

 employed to scrub the wheat. (2) The cleaned 



y 

 B 



wheat is sent to grooved chilled-iron rollers (see 

 fig. 1 ), and slightly broken between them ; the 

 product is sifted by means of cylinders covered 

 with wire-cloth or silk-gauze, by" which means a 

 proportion of Hour is separated, mixed with a sub- 

 stance composed of small pieces of the floury part 

 of the wheat berrv, and called usually ' middlings,' 

 sometimes ' semolina. ' The pieces of broken wheat 

 are sent to other rollers to be again broken, and the 

 product sifted as before. This process is repeated 

 from four to seven times, according to the ideas of 

 the miller and the nature of the wheat, until, as 

 far as possible, all the floury part has been scraped 

 from the husk or ' bran,' which is sold for fodder. 



Fig. 1. Roller Mill. 



We are thus left with the mixture of flour and 

 'middlings' from the four to seven breaking pro- 

 cesses. The products from the different breaking 

 processes are generally mixed together and then 

 sifted as before described, in order to separate 

 the flour which is then ready for use from the 

 ' middlings,' which are then put through the pro- 

 cess called ' purification.' It may here lie mentioned 

 that the making of a large quantity of 'middlings' 

 is the principal difference between the former 

 'low-grinding and the present ' high -grinding' 

 system, and is the chief advantage of the latter. 

 By the former process it was sought to reduce 

 the wheat at one grinding as far as possible 

 into flour and bran : it was, however, found to be 

 impossible to keep the two separate, a portion of 

 finely-powdered bran tain" inevitably mixed with 

 the flour, greatly to the detriment of the latter. 

 By high-grinding, the floury part is reduced in the 

 first instance principally to a granular state, and, 

 though bran particles are mixed with the flour 

 granules, they may be almost entirely separated, 

 owing to the difference in their specific gravity, by 

 means of this process of purification. ( 3 ) The size 

 of the granules of the middlings varies from that of 

 fine sand to that of a pin's head. The middlings 

 are therefore first separated by sifting into as many 

 sizes as may be thought desirable, and each size 

 is sent to one or more machines called 'middlings' 

 purifiers.' These are of two types, called 'gravity' 

 and 'sieve' purifiers. In the first type, which is 

 generally used for the large sixes of middlings, the 

 material is directly acted on by a draught of air. 

 The machine usually takes the form of a series of 

 sloping Ixmrds, or of revolving discs, by either of 

 which devices the middlings are caused to fall 

 repeatedly in a thin even stream through a current 

 of air produced by a revolving fan. As the specific 

 gravity of the flour granules is greater than that of 

 the bran particles, it is obvious that the current of 

 air may be so regulated as to carry away the par- 

 ticles of bran, leaving the flour granules to fall to 

 the bottom of the machine. 



The sieve purifier generally takes the form of an 

 oblong box, or case, of wood ; occupying the centre 



