RAZORS 693 



VEXWT, in mining. A. vein cutting indifferently through all the strata ; 

 under aome circumstances they are known as gash veins and slip veins. 



RAM, HYDRATTMC. Originally invented by Montgolfier, in France, and 

 patented by him in 1797. 



This machine, which is self-acting, is composed of an air-vessel and 3 valves, 2 for 

 the water and 1 for keeping up the supply of air. Upon pressing down the valve in 

 the conducting tube, wnich opens downwards, the water escapes from it, until this 

 momentum is sufficient to overcome the weight, when the valve immediately rises 

 and closes the aperture. The water, having then no other outlet than the inner 

 valve, rushes through it by its general force, compressing the air in the air-vessel 

 until equilibrium takes place, when the air reacts by its expansive force, closing the 

 inner valve, which retains the water above it, and driving it up the ascending tube. 

 By this reaction the water is forced back along the conducting-pipe, producing a 

 partial vacuum beneath the outer valve, which immediately falls by its own weight. 

 The water thus escapes until it has acquired sufficient force to close this, when the 

 action proceeds as before. It is best adapted for raising moderate quantities of water, 

 as- for household or farming purposes. 



RAMMERS. In mining, an instrument used for compressing the powder in the 

 hole for blasting. In engineering, the tool used for ramming earth, clay, or loam, in 

 making dams and the like. 



RAPE-SEED. (Brassica campcstris oleifera.) Summer Rape, Wild Navew, or 

 Colza. This and the winter rape (B. Napus) are the only sorts cultivated to any 

 extent in Britain for the manufacture of oil, and growers generally agree that the 

 former of these is to be preferred from its yielding a greater quantity of seed, in the 

 proportion of 955 to 700. (Lawson.) See COLZA. 



RAPE-SEED Oil.. See OILS. 



RASPS AND FIXiES. File-making is a manufacture which is still in a great 

 measure confined to Sheffield. It is remarkable that hitherto no machine has been 

 constructed capable of producing files which equal those cut by the human hand. 

 Machine-made files have not the 'bite' which hand-cut files have : this is accounted 

 for by the peculiar facilities of the human wrist to accommodate itself to the particular 

 angle suitable to produce the proper ' cut.' Small files are made out of the best cast 

 steel ; those of a larger size from ordinary steel ; flat files are forged on an ordinary 

 study; other forms on bolsters, with the indentature corresponding to the shape 

 required being thereon impressed : a chisel wider than the blank to be cut is used as 

 the only instrument to form the teeth ; it is moved by the hand with the greatest 

 nicety. After cutting, and previous to hardening, the file is immersed in some adhesive 

 substance, such as ale-grounds, in which salt has been dissolved ; this protects the 

 teeth from the direct action of the fire ; it is then immersed perpendicularly in water ; 

 cleaned, and finished. 



The manufacture of rasps and files does not belong to this work. Those interested 

 in it will find an elaborate description of all the varieties of files, and of their manu- 

 facture, in ' Turning and Mechanical Manipulation,' by Holtzapffel ; and in ' Manu- 

 factures in Metal,' vol. i., Iron and Steel, revised by Mr. Eobert Hunt. 



RASP, IVXECHANICAIi, is the name given by the French to an important 

 machine much used for mashing beet-roots. See SUGAR. 



RATAFIA is the generic name, in France, of liqueurs compounded with alcohol, 

 sugar, and the odoriferous or flavouring principles of vegetables. Bruised cherries with 

 their stones are infused in spirit of wine to make the ratafia of Grenoble de Teyssere. 

 The liquor being boiled and filtered, is flavoured when cold with spirit of noyeau, 

 made by distilling water off the bruised bitter kernels of apricots, and mixing it with 

 alcohol. Syrup of bay laurel and galango are also added. See LIQUEURS. 



RATTANS. The stems of the Calamus rotang, of C. rudentum, and various 

 species of palms. They are used for caning chairs, as a substitute for whalebone, for 

 walking-sticks, and many other purposes. 



RAZORS. The manufacture of razors differs from the manufacture of the finer 

 varieties of cutting instruments, only in the degree of care which is required to pro- 

 duce a perfect instrument. 



Two workmen are always engaged in razor-making. The rod of steel of which 

 they are made is about half an inch in breadth, and of sufficient thickness to form the 

 back. The stake upon which they are forged is rounded on both sides of the tops, 

 which is instrumental in thinning the edge, and much facilitates the operation of 

 grinding. The blades are then hardened and tempered in the ordinary way, with the 

 exception that they are placed on their back on an iron plate, and the moment they 

 assume a straw colour of a deep shade they are removed. 



The grinding follows, on a stone revolving in water ; then glazing on a wooden disc. 

 The fine polish is given by a wooden wheel, having ifs circumference covered with 



