406 



BLOWPIPE 



convenient for the purpose), and as long as the reed trough, is to be stuck with common 

 paste on the face of a carpenter's rule, or, in preference, that of an exciseman, as tho 

 inches are divided into tenths instead of eighths ; in either case observing that tho 

 divisions of the inch on the rule be left uncovered by the paper. When it is dry, 

 lines must be drawn tho whole length of it, |th inch apart, to mark out a stripe th 

 inch wide. Upon this stripe the divisions of the inch are to be ruled off by means of 

 a small square. 



The centre divsion being marked 0, it is to be numbered at every fourth line to the 

 ends. Thus the fourth from the centre on each side will bo 10 ; the eighth, 20 ; tho 

 twelfth, 30 ; the sixteenth, 40, &c. ; and a slip 10 inches long, graduated into 

 tenths of an inch, will have on each arm 50 lines, or 125 degrees, divided by these 

 lines into quarters. While the lines and numbers are drying, the exact centre of tho 

 reed-trough may be ascertained, and marked right across, by spots on the two edges. 

 A lino of gum-water, full |th inch wide, is then laid with a camel-hair pencil along tho 

 hollow, and the paper being stripped from the rule (which it leaves easily), the gra- 

 duated stripe is cut out with scissors, and laid in the trough, with the line exactly in 

 the centre. Being pressed to the gummed reed, by passing tho round end of a quill 

 along it, it graduates the trough from the centre to each end. This graduation is very 

 true, if well managed, as the paper does not stretch with the gum-water after being 

 laid on the rule with the paste. 



A very fine needle is next to be procured (those called bead-needles are the finest) 

 and passed through a slip of cork tho width of the centre of the trough, about th 

 inch square, |th thick. It should be passed through with care, so as to be quite 

 straight. The cork should then be cut until one end of it fits into the trough, so that 

 the needle shall bear on the edges exactly in the spots that mark the centre, as it is 

 of importance that the needle and the trough be exactly at right angles with each 

 other. The cork is now to be fixed in its place with gum-water, and, when fast dry, 

 to bo soldered down on each side with a small portion of any soft resinous cement, on 

 the point of a wire or knitting-needle ; a little cement being also applied in the same 

 manner to the edges of the cork whore the needle goes through, to give it firmness, 

 the beam is finished. It may be balanced by paring the edges on the heaviest side : 

 but accurate adjustment is needless, as it is subject to vary with the dampness or dry- 

 ness of the air. 



The support on which it plays is a bit of tin plate (or, in preference, brass plate), 

 Ifths inch long, and 1 inch wide. The two ends are turned up square fths of an 

 inch, giving a base of ths of an inch wide, and two upright sides |ths high. The 

 upper edges are then rubbed down smooth and square upon a Turkey stone, letting 

 both edges bear on the stone together that they may exactly correspond. For use, tho 

 beam is placed evenly in tho support, with the needle resting across the edges. Being 

 brought to an exact balance by a bit of writing-paper, or any other substance, placed 

 on the lighter side, and moved toward the end until the equilibrium is produced, it 

 will turn with extreme delicacy, a bit of horsehair, |th inch long, being sufficient to 

 bring it down freely. 



It must not be supposed that any such instrument as this is recommended as in any 

 way substituting the beautiful balances which are constructed for the chemist, and 

 others requiring to weigh with great accuracy. The object is merely to show the 

 miner a method by which he may construct for himself a balance which shall be suf- 

 ficiently accurate for such blowpipe investigations as it may be important for him to 

 learn to perform for himself. If the suggestions of the chemist who devised the above 

 balance had been carried out, much valuable mineral matter which has been lost might 

 have been turned to profitable account. 



The blowpipe is largely used in manufactures, as in soldering, in hardening, and 

 tempering small tools, in glass-blowing, and in enamelling. In many cases the blow- 

 pipes are used in the mouth, but frequently they are supplied with air from a bellows 

 moved by the foot, by vessels in which air is condensed, or by means of pneumatic 

 apparatus. 



A simple form of regulator for giving a perfectly constant blast has lately been 

 devised by Messrs, Armin, Junge, and Mitzopulos, of Freiburg. The apparatus is thus 



