ANGORA WOOL 175 



mine, as indicated by a water-gauge fixed in the mine ia the usual way, is 3 inches, 

 and becomes as low as 0'7 inches when the furnaces are out for repairs to the shaft. 



4 The dotted line on the preceding diagram (fig. 69) exhibits the range of the 

 water-gauge readings, placed in the ordinary position in the mine between the upcast 

 and downcast shafts, taken one each day for a fortnight. The black line exhibits the 

 readings of the water-gauge placed in the colliery office, by means of a pipe from the 

 bottom of the downcast shaft, on the principle previously explained. 



' The office is 200 yards distant from the top of the pit, which is 508 yards deep ; 

 there is, therefore, 708 yards of pipe (in this case the ordinary half-inch gas-pipe). 



'It will be observed that in the customary application of the water-gauge, the 

 height of the water-column due to the ventilating pressure is 3 inches, falling to 0'7 

 inches when the furnaces are out, being a range of little more than 2 inches ; whilst in 

 the new application, the ordinary reading is 5 inches, falling to a minimum of 1'5 

 inches, having, therefore, a range of 3 g 5 inches, or nearly double. 



' By the addition of a galvanic battery the instrument could be made, if this be 

 considered advisable, to ring a bell when the pressure became reduced below a fixed 

 point.' 



ANEROID BAROMETER. This instrument was invented by M. Vidi, of 

 Paris. In its latest form it consists of a cylindrical case, about 4 or 6 inches in 

 diameter, and 2 inches deep, in which lies a thin metal box, near to, and parallel 

 with, the curved boundary of the case, its two ends being distant about half an incli 

 from each other. From this box the air 

 has been partially exhausted, and the 

 pressure of the external atmosphere on 

 it causes it to alter its form. The ac- 

 companying figure (70) shows a section 

 of this box. It is made of thin cor- 

 rugated plates of metal, so that its 



elasticity is great. By means of the .... , 



tube F, the air is partially exhausted, L-r^T 



when the box takes the form shown by the dotted lines. A small quantity of gas is 

 introduced after exhaustion, the object of which is to compensate for the varying 

 elasticity of the metal at different temperatures. The pressure of the air on the box 

 in ordinary instruments is between 40 and 50 Ibs., and it will easily be understood 

 that any variation in this pressure will occasion the distances between the two plates 

 to vary, and consequently the stalk will have a free motion in or out. This is, by an 

 ingenious contrivance, changed from a vertical motion to a motion parallel to the face 

 of the dial, and this is converted into a rotatory one by the application of a watch-chain 

 to a small cylinder or drum. The original very slight motion is augmented by the aid 

 of levers. This is so effectually done, that when the corrugated surfaces move through 

 only the 250th part of an inch, the index-hand on the face turns over a space of three 

 inches. The extreme portability of this little instrument, and its comparative freedom 

 from risk of injury, render it exceedingly useful to the traveller. Its accuracy 

 is proved by the experiments of Professor Lloyd, who placed ono under the re- 

 ceiver of an air-pump, and found that its indications corresponded with those of 

 the mercurial gauge to less than O'Ol of an inch ; and within ordinary variations 

 of atmospheric pressure the coincidences are very remarkable. Lloyd, Nichol, Dreiv. 

 See BAEOMETEE. 



ANETHTJM GRAVEOXiENS. The common garden Dill. This plant is cul- 

 tivated in England and imported from the South of Europe. It is used medicinally 

 chiefly on account of its hot and sweetish taste, and for flavouring spirituous cordials. 



ANGEXiXCA. (Angelique, Fr. ; Angdika, Ger.) The Archangelica ojficinalis. 

 The dried angelica root is imported from Hamburg in casks. The tender stems, 

 stalks, and the midribs of the leaves, are made, with sugar, into a sweetmeat (candied 

 angelica). The angelica root and seeds are used by rectifiers and compounders in the 

 preparation of gin, and as an aromatic flavouring for ' bitters." The quantity culti- 

 vated in some moist places in this country is sufficient to meet our requirements. 



ANGXjE-IRON. A piece of iron rolled out in the shape of to form joints. 



ANGLE-RAFTER or HIP-RAFTER. A piece of timber which runs from 

 the angle of the building to the ridge of the roof, into which it is framed. 



ANGXiE-STAFF. Strips of wood placed upon the vertical angles to protect the 

 plastering. 



ANGXiESXTE. A sulphate of lead found native, generally produced by the 

 decomposition of galena (sulphide of lead). It was first found at Pary's mine in 

 Anglesea, whence the name. 



ANGORA WOOL. (Foil de chevron d 1 Angora, Fr.) Called also angola and 

 angona. The wool of the Angora goat (Capra Angorensis), employed in the nianu- 



