244 MILL-STONE 



60-horse power and fitting-up, 3,000 dols. ; 1 pump for boiler, 100 dols. ; outside 

 water-pipes, 500 dols. ; 1 cooling tank for receiving and storage, 500 dols. ; 1 heating 

 tank and pipes for milk, 300 dols. ; hot water tank and steam-pipes for washing cans 

 and 2 rinsing sinks, 600 dols. ; 1 steamer-bath for scalding cans and pipes, 150 dols. 



It will be seen from the above, that a well-furnished factory, with all the needful 

 appliances, is somewhat expensive ; but the profits from the business are also con- 

 siderable. The cost of condensing will probably be no more than one-half per cent, 

 per quart. It takes about 3 pints of milk to make 1 Ib. of the sugared condensed 

 milk, which sells in the market for 25 cents and upward. It is not easy to give the 

 exact cost of condensing, since that will depend upon the amount of milk worked and 

 the economy with which the factory is managed ; but we should say that Id. per quart 

 ought to cover all the expenses for condensing. The cans, and the labour of filling 

 and soldering, are an additional expense, which our readers can figure approxi- 

 mately, so that some idea of the profits may be obtained. 



There are two kinds of condensed milk in the market : the sugared, as above 

 described, and which will keep for long periods, and the plain condensed milk, which 

 contains no sugar, and is sold for immediate use. This last will only keep sound-for a 

 few days. It is made in the same way as the other, except that no sugar is used in its 

 manufacture. A less price is obtained for it in the market than for sugared milk, it 

 being sold by the quart from large carrying cans, and regularly furnished to consumers 

 from time to time. 



One great difficulty in the way of establishing new factories, is in obtaining skilled 

 workmen to conduct the business of condensing. There are comparatively few persons 

 who have had experience in the work of a factory, and these are, for the most part, 

 retained by these factories now in successful work. As these factories have built up 

 a good trade and have a ' good thing,' they do not care to open their doors for in- 

 struction or to educate any person in the business who would engage in a new factory. 

 In cheese-making or in butter-making there are always plenty of skilled hands to be 

 had, but the case is quite different in the condensing business, and this fact has de- 

 terred many from entering upon the work. 



MXIiXi, THE. A name given to the cylinder used by the calico-printers, in which 

 the impression is obtained by a process like that of a milling tool, from a cylinder 

 engraved by hand, called the Die. See CALICO-PRINTING. 



IMCXIiZi-STOWZ:, or Buhr-Stone. This interesting form of silica, which occurs in 

 great masses, has a texture essentially cellular, the cells being irregular in number, 

 shape, and size, and are often crossed by thin plates, or coarse fibres of silex. The 

 buhr-stone has a straight fracture, but it is not so brittle as flint, though its hardness 

 is nearly the same. It is feebly translucent ; its colours are pale and dead, of a whitish, 

 greyish, or yellowish cast, sometimes with a tinge of blue. 



The Buhr-stones usually occur in beds, which are sometimes continuous, and at 

 others interrupted. These beds are placed amid deposits of sand, or argillaceous and 

 ferruginous marls, which penetrate between them, filling their fissures and honeycomb 

 cavities. Buhr-stones constitute a very rare geological formation, being found in 

 abundance only in the mineral basin of Paris, and a few adjoining districts. Its geo- 

 logical position is well ascertained : it forms a part of the lacustrine, or fresh-water 

 formation, which, in the locality alluded to, lies above the upper eocene gypsum, and the 

 stratum of sand and marine sandstone which cover it. Buhr-stone constitutes, there- 

 fore, in the locality in which it is found, the uppermost solid stratum of the crust of 

 the globe ; for above it there is nothing but alluvial soil, or diluvial gravel, sand, and 

 loam. 



Buhr-stones sometimes contain no organic forms ; at others they seem as if stuffed 

 full of fresh-water shells, or land-shells and vegetables of inland growth. There is no 

 exception known to this arrangement; but the shells have assumed a siliceous nature, 

 and their cavities are often filled with crystals of quartz. The best buhr-stones 

 for grinding corn have about an equal proportion of solid matter and of vacant space. 

 The finest quarry of them is upon the high ground, near La Ferte sous Jouarre. The 

 stones are quarried in the open air, and are cut out in cylinders from one to two 

 yards in diameter, by a series of iron and wooden wedges, gradually but equally in- 

 serted. The pieces of buhr-stones are afterwards cut into parallelopideds, called panes, 

 which are bound with iron hoops into large millstones. These pieces are exported 

 chiefly to England and America. Good millstones of a bluish-white colour, with a 

 regular proportion of cells, when 6^ feet in diameter, fetch 1,200 francs apiece or 48/. 

 sterling. A coarse conglomerate "sandstone or breccia is, in some cases, used as a 

 substitute for buhr-stones ; but it is a poor one. 



In addition to the French buhr-stone, other materials are employed as millstones. 

 Thus the lava of Niedermendig, near Andernach, on the Rhine, has been extensively 

 worked as a millstone since the time of the Romans. This lava is a nepheline 



