BLAST-HOLES 361 



water again, and wash and work for an hour in a bath of 30 Ibs. of logwood and 10 Ibs. 

 of fustic; lift, and add 2 Ibs. of copperas, and work 30 minutes longer, and finish. 



BLACK. FLUX. Seo ASSAYING. 



BLACK, HJEMATITE. An ore of MANGANESE. 



BLACKING FOR SHOES. (Cirage des bottes, Fr. ; Schuhschwarze, Ger.) 

 Blacking consists of a black colouring-matter, generally bone-black, and substances 

 that acquire a gloss by friction, such as sugar and oil. The usual method is to mix 

 the bone-black with sperm-oil ; sugar, or molasses, with a little vinegar, is then well 

 stirred in, and strong sulphuric acid is added gradually. The acid produces sulphate 

 of lime and acid phosphate of lime, which is soluble : a tenacious paste is formed by 

 these ingredients, which can bo smoothly spread ; the oil serving to render the leather 

 pliable. This forms a liquid blacking. Paste blacking contains less vinegar. In 

 Germany, according to Liebig, blacking is made by mixing bone-black with half its 

 weight of molasses, and one-eighth of its weight of hydrochloric acid, and one-fourth 

 of its weight of strong sulphuric acid, mixing with water, to form an unctuous paste. 

 The following method for making liquid and paste blacking is given by William 

 Bryant and Edward James : 18 ounces of caoutchouc are to be dissolved in about 

 9 Ibs. of hot rape-oil. To this solution 60 Ibs. of fine ivory-black and 45 Ibs. of 

 molasses are to be added, along with 1 Ib. of finely ground gum arabic, previously 

 dissolved in 20 gallons of vinegar of strength No. 24. These mixed ingredients are 

 to be finely triturated in a paint-mill till the mixture becomes perfectly smooth. To 

 this varnish 12 Ibs. of sulphuric acid are to bo now added in small successive quan- 

 tities, with powerful stirring for half an hour. The blacking thus compounded is 

 allowed to stand for 14 days, it being stirred half an hour daily ; at the end of which 

 time 3 Ibs. of finely ground gum arabic are added ; after which the stirring is re- 

 peated half an hour every day for 14 days longer, when the liquid blacking is ready 

 for use. In making the paste blacking, the patentees prescribe the above quantity of 

 india-rubber oil, ivory-black, molasses, and gum arabic, the latter being dissolved in 

 only 12 Ibs. of vinegar. These ingredients are to be well mixed and then ground 

 together in a mill till they form a perfectly smooth paste. To this paste 12 Ibs. of 

 sulphuric acid are to be added in small quantities at a time, with powerful stirring, 

 which is to be continued for half an hour after the last portion of the acid has been 

 introduced. This paste will be found fit for use in about seven days. 



BLACK-JACK. The miner's name for blende, or sulphide of zinc. See ZINC. 



BLACK. Li: AD. The common name of PLUMBAGO or GRAPHITE. 



BLACK-LEAD PENCILS. See PENCIL MANUFACTURE. 



BLACK TIN. The miner's name for tin ore ready for the smelter. See TIN. 



BLACK WADD. One of the ores of manganese. See MANGANESE. 



BLADDER. ( Vessie, Fr. ; Blase, Ger.) A bag or sack, in animals, which serves 

 as the receptacle of some secreted fluid. Bladders are chiefly employed for securing 

 jars, bottles, &c. 



BLANKET. (Blanchet. Fr.) A cover for a bed made of coarse wool loosely 

 woven. Among printers the woollen cloth which is placed between the tympans is 

 called a blanket. 



Blankets are largely used in Californian gold-quartz mining, for catching the par- 

 ticles of metal as they escape from the stamping mill. These blankets are generally 

 of a coarse grey wool, and are woven expressly for the miner, at the woollen mills on 

 the coast. They are made about 30 inches wide, and are spread over blanket-boards, 

 or shallow wooden troughs, each about 16 inches wide, 3 inches deep, and from 9 to 

 12 feet long, and inclined in the direction of their length at an angle of from 3 or 4 

 to 15 to the horizon. The finely pulverised ore, suspended in water, is carried in a 

 current, from the battery-box, over the surface of a series of these blankets. In this 

 way a larger proportion of the gold and auriferous pyrites, or of the gold-amalgam if 

 mercury has been used in the battery, becomes entangled in the fibres of the fabric. 

 Any particles that may escape are finally retained by a system of amalgamated copper 

 riffles over which the current of water is generally caused to flow after leaving the 

 blankets. The blankets, charged with finely-divided metal, are frequently washed 

 (the upper ones, on which the heaviest sand is deposited, being in some cases washed 

 every quarter of an hour), and the residue from the washings is then amalgamated. 

 It has been attempted, but without success, to substitute ox-hides or sheepskins for 

 the blankets. See WOOLLEN MANUFACTURES. 



BLAST. The current of air driven into a furnace ; it may be either cold or hot 

 air. See HOT BLAST. 



BLAST-FURNACE. A furnace into which air is forcibly blown. See IRON, 

 METALLURGY. 



BLAST-HOLES. A mining term. The holes through which. the water enters 

 the bottom of a pump in tho mines. 



