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ANEMOMETER 



apparatus, -which is of such frequent occurrence -with the ordinary form of -water- 

 gauge. The tube is contracted at the bottom bend to prevent the oscillations of the 

 water-column, especially when used near the ventilating shafts ; in the original ane- 

 mometer of Dr. Lind, which was similar in principle to the water-gauge, this con- 

 traction was used. 



' The tubes are fitted to the surface of a flat piece of wood, which entirely prevents 

 liability to fracture, and the apparatus can safely bo carried in the pocket ; a small 

 bulb-tube is fixed to the wood to allow of it being adjusted perfectly level when in use, 

 and this is of considerable importance, for any deviation from the perpendicular is 

 attended with an alteration in the level of the liquid in each tube. When in use, tho 

 writer generally mixes a drop of tincture of rosaniline in the water : with this the 

 position of tho surface of the water in each tube is clearly distinguished, and the specific 

 gravity of the fluid not appreciably altered. 



Where any great accuracy is required, a vernier, worked by another threaded 

 screw, could readily be attached to tho present scale.' 



A new application of the water-gauge for ascertaining the pressure of tho ventilating 

 column in mines was made by Mr. John Daglish : 



' The ordinary mode of using the water-gauge in mines, for ascertaining tho ventilating 

 pressure, is to place it between the intake and return currents, as near as possible to 

 the bottom of the shaft in the mine. The water-gauge, however, placed in this 

 position, does not give the actual difference of pressure due to tho differences of tho 

 weight of the downcast and upcast columns of air at their different temperatures, but 

 only the excess of this amount of pressure over the pressure absorbed by the friction of 

 the currents in the shafts. 



'This loss of pressure from shaft-friction in deep pits, especially where largo 

 quantities of air are moving at high velocities in the shafts, reaches a considerable 

 amount, and very sensibly reduces the indications of the water-gaugo as ordinarily 

 employed. By placing in the downcast shaft, however, a range of pipes closed at the 

 lower end by being connected to one leg of a water-gauge, the other leg being open to 

 the upcast shaft, the loss of pressure due to the friction of the air passing down tho 

 downcast slutft is avoided, and thus not only is the advantage gained of a greater 

 difference in the level of tho water in the two tubes than exists under ordinary cir- 

 cumstances, and thereby enabling the existing state of the ventilating pressure to be 

 more easily observed and recorded ; but inasmuch as tho velocity in the downcast shaft 

 diminishes with a diminished temperature of the upcast shaft, the increased difference 

 of level referred to above is not a constant quantity, but also varies with tho heat of 

 the upcast shaft ; hence, a water-gaugo so fixed, not only gives a greater extent of 

 scale under the ordinary state of the ventilation of the mine, but also a greater range 

 of scale under variation of temperature. 



' Another advantage gained by this motla of using a water-gauge is its freedom from 

 the momentary oscillations which are so objectionable in the water-gauge as ordiuurily 

 used, and which prevent very accurate readings. 



4 But the chief benefit to be derived from the application of a long range of tubes in 

 the downcast shaft, is that of being able to place the water-gauge on the surface in any 

 position that may be most desirable, as its action is not interfered with by extending 

 the pipes to any length or in any direction, inasmuch as the column of air in tho pipo 

 is dormant and its pressure consequently not reduced by friction. 



' At Seaton Colliery, belonging to Earl Vane, the depth of the shaft is 25 1 fathoms 

 to the furnace in the Hutton-seam; the upcast shaft is 14 feet in diameter, and tho 

 quantity of air going down the downcast shaft is 200,000 cubic feet per minute, and 



69 



this quantity becomes increased to 300,000 cubic feet per minute in the upcast shaft 

 by expansion duo to the high temperature. The ordinary ventilating pressure of the 



