MILK MILL. 



817 



and field-officers of their respective divisions, until 

 otherwise directed by law. General and field-officers 

 appoint their staff-officers. The governor appoints 

 an adjutant-general, and all other militia officers 

 whose appointments are not otherwise provided for. 

 In Maine, the system is much as in the last mentioned 

 state, except that the major-generals are elected by 

 the senate and house of representatives. The con- 

 stitutions of some of the states exempt from militia 

 duty, with more or less qualification, persons con- 

 scientiously scrupulous about bearing arms. This is 

 the case with those of Maine, New Hampshire, New 

 York, Pennsylvania r Tennessee, Indiana, Missouri, 

 Illinois, Alabama. See Army, and Army, Standing. 

 MILK; a secretion peculiar to the females of the 

 class mammalia, or those animals which feed their 

 young from their teats, and which takes place, in 

 some of them, only during and after the time of ges- 

 tation. It differs as procured from different animals, 

 but its general properties are the same in all. When 

 this fluid is allowed to stand for some time, it under- 

 goes spontaneous changes, and is resolved into its 

 component parts : a thick yellowish substance 

 collects on the surface, which is called cream, 

 and the milk beneath becomes thinner than before, 

 and is of a pale bluish colour. When cream 

 is kept for some days without being disturbed, it 

 gradually becomes thicker, till at last it acquires the 

 consistence of cheese; and hence one method of 

 making cream-cheese, merely by putting cream into 

 a linen bag, and leaving it there till it becomes solid. 

 When cream is shaken, it is resolved into its compon- 

 ent parts. The process by which this is accomplished 

 is called churning, by which two substances are ob- 

 tained, butter and butter-milk. In the making of 

 butter, cream is allowed to stand for some time, dur- 

 ing which an acid is generated. It is then put into 

 a churn and shaken, by which the butter is grad- 

 ually separated. What is left (the butter-milk) has 

 a sour taste, but by no means so much so as that of 

 the cream before the churning. Butter is sometimes 

 also made from cream which has not become sour, 

 but the process is much more tedious, the acid formed 

 in the other case favouring its separation. Butter is 

 merely an animal oil, solid at a natural heat, but held 

 in solution in milk, by some of the other substances. 

 As thus procured, it is not pure, but may in a great 

 measure be freed from its impurities, by washing it 

 with cold water ; and though apt to become rancid, 

 yet, when mixed with salt, may be kept any length 

 of time. Milk from which butter has been taken, 

 undergoes spontaneous changes. It becomes much 

 sonrer, and congeals into a mass of the consistence of 

 jelly. When heated, the fermentation of this coagu- 

 lum is hastened, and by the addition of certain sub- 

 stances, it very soon takes place; thus acids and 

 spirit of wine curdle it, which is owing to the albu- 

 men it contains being acted on by them, in the 

 same way as blood or white of eggs. By far the 

 most powerful coagulator, however, is the substance 

 called rennet, which is the decoction of the stomach 

 of animals, as a calf. When the milk is previously 

 heated, and rennet added, it is almost instantly 

 coagulated. If after this it is cut, a thinnish fluid 

 oozes from it, and if it be put into a bag and squeezed, 

 the whole of this is forced out, and a whitish, tough 

 matter is left ; the former is whey, the latter curd. 

 On this depends the process of making cheese, which 

 varies in richness, according to the mode followed in 

 preparing it. When milk is heated gradually, and 

 merely to the temperature at which it curdles, and if 

 the curd be freed gently from the whey, it retains 

 almost the whole of the cream, which adds to its 

 richness and flavour. But when it is curdled quickly, 

 and the whey is speedily removed by cutting the curd, 



a great deal, or nearly the whole of the cream is car- 

 ried off, and the cheese is poor, and has not the rich 

 flavour of that made in the other way. In making 

 cheese, having obtained the curd, and freed it from its 

 whey, the remaining part of the process is merely to 

 subject it to pressure, by which the whole of the whey 

 is forced out, the colour being communicated by the 

 addition of colouring matter : that generally used is 

 annotta, which is mixed with the milk. Whey has a 

 pleasant taste, and contains a considerable quantity 

 of a sweetish substance, called sugar of milk ; hence 

 it is frequently used as drink, and from its nutritious 

 quality, it is administered to delicate people ; hence 

 the use of asses' milk, which contains a large quantity 

 of it. It is from its containing this saccharine mat- 

 ter, that it is sometimes, as in some of the northern 

 counties of Scotland, made to undergo fermentation, 

 by which a very weak spirituous fluid is obtained. 

 By evaporation it affords a minute quantity of saline 

 matter and a considerable portion of sugar of milk. 

 When whey or milk is exposed to a temperature 

 between 60 and 80 it undergoes a spontaneous 

 change, attended by the production of an acid, which 

 was originally examined by Scheele, and has been 

 termed lactic acid. 



MILKY WAY. See Galaxy. 



MILL ; originally, a machine, adapted to divide, 

 crush, or pulverize any substance; but more exten- 

 sively applied, in modern times, to almost all ma- 

 chinery consisting of wheel work, whether intended 

 to change the form, or merely the position of the 

 substance operated upon. The term as thus used is 

 very indefinite, both in regard to the moving power 

 and the application of the power or the pro- 

 cess. Mills therefore take different names, from 

 the process, as stamping-mills, saw-mills, ful- 

 ling-mills, grinding-mills, &c. ; from the moving 

 power, as wind-mills, water-mills, hand-mills, steam- 

 mills, &c.; or from the material operated upon, as cot- 

 ton-mills, flour-mills, sugar-mills, oil-mills, &c. This 

 ^Peat variety in the nature and uses of mills renders it 

 impossible to give descriptions of them under one 

 head. The general principles of the machinery and 

 the moving powers will be found described under the 

 heads Mechanics, Hydrodynamics, Machinery, Pneu- 

 matics, Steam, Wheels, &c., and their particular appli- 

 cations to different materials will be treated of under 

 the appropriate heads. One of the earliest and most 

 universal applications of machinery of this kind is to 

 the comminution of grain . Among the rudest nations 

 we find this done by pounding it between two stones; 

 but with the first advances of art, a simple hand-mill 

 is constructed, composed of an immovable nether- 

 stone (Gr. p,v\i>) and an upper-stone (pu\o! or <), 

 put in motion by the hand. These machines were 

 used by the Hebrews and Greeks, and commonly 

 moved by slaves or criminals. Asses were after- 

 wards employed. According to the Greek mythology 

 Pilumnus, Myles, or Mylantes, invented the milL 

 Water-mills (molae aquariee) seem to have been used 

 by the Romans. Wind-mills were invented in the 

 time of Augustus. Among the moderns the common 

 mill for grinding grain is constructed with two circu- 

 lar stones placed horizontally. Buhr-stone is the best 

 material of which mill-stones are made, but sienite 

 and granite are frequently used. The lower stone is 

 fixed, while the upper one revolves with considerable 

 velocity, and is supported by an axis passing through 

 the lower stone, the distance between the two being 

 capable of adjustment according to the fineness which 

 it is intended to produce in the meal or flour. When 

 the diameter is five feet, the stone may make about 

 ninety revolutions in a minute without the flour becom- 

 ing too much heated. The corn or grain is shaken out 

 ofa hopper by means of projections from the revolv- 

 3 F 



