VERDIGRIS 



1071 



serve a thorough closing of the top of the shaft. The flaps were to be opened again 

 by a lever from the top to allow the cage to descend. However, it was found on trial 

 that the valve K at the top was amply sufficient ; and consequently, although the 

 other valves were also provided, they were never put into use. 



The total depth of the pit is nearly 300 yards, and at a depth of 120 yards a split 

 of air is taken off, and coursed through workings from which coal and fire-clay are 

 got ; the larger portion of the air descends to the bottom of the pit, and is there split 

 into many courses, to work two separate seams of coal and a vein of ironstone. The 

 total length of road laid with plates or rails in the workings is about 7 miles, and the 

 working faces amount to nearly double that distance. The longest distance that is 

 traversed by any single course or split of air in passing from the downcast to the 

 upcast shaft is nearly 2 miles. The quantity of materials raised from the pit is about 

 500 tons daily. 



The following Table gives the results of a series of experiments made with this 

 ventilating fan by Mr. E. S. Roper, showing that the quantity of air delivered at the 

 velocities of 60 and 80 revolutions of the fan per minute is 45,000 and 56,000 cubic 

 feet per minute, with a velocity of current of 782 and 1,037 lineal feet per minute 

 respectively, or about 9 and 12 miles per hour; and the degree of vacuum or ex- 

 haustion in the upcast shaft is '5 and - 9 inch of water respectively. 



Synopsis of Experiments on Fan Ventilation. 



The speed at which the ventilating fan is usually worked is about 60 revolutions per 

 minute, giving a velocity at the circumference of the fan of 2,545 feet per minute ; 

 45,000 cubic feet of air per minute are then drawn through the mine, nearly one-third 

 of which ventilates the upper workings, and the rest passes through the lower 

 workings. 



The Guibal fan especially has been used in several collieries. 



Several modified forms of fan ventilation have been introduced, but the principle 

 involved is essentially the same in all. 



VERANTIWE. See MADDER. 



VERATRINE. C 64 H 52 N 2 16 (C^H^JTO 8 ). An alkaloid contained in white 

 hellebore ( Vcratrum album), and in cevadilla ( V. Sabadilla). It is exceedingly 

 poisonous, and if introduced into the nostrils excites violent and prolonged sneezing. 

 In the form of ointment it has been found a valuable remedy in neuralgic disorders. 



VERDIGRIS. (Vert-de-gris, Fr. ; Griinspan, Ger.) The copper used in this 

 manufacture is formed into round sheets, from 20 to 25 inches diameter, by one- 

 twenty-fourth of an inch in thickness. Each sheet is then divided into oblong squares, 

 from 4 to 6 inches in length, by 3 broad ; and weighing about 4 ounces. They ar ' 

 separately beaten upon an anvil, to smooth their surfaces, to consolidate the metal, 

 and to free it from scales. The refuse of the grapes, after the extraction of th^ir 

 juice, formerly thrown on to the dunghill, is now preserved for the purpose of making 

 verdigris. It is put loosely into earthen vessels, which are usually 16 inches high. 

 14 in diameter at the widest part, and about 12 at the mouth. The vessels are then 

 covered with lids, which are surrounded by straw mats. In this situation the materials 

 soon become heated, and exhale an acid odour ; the fermentation beginning at tho 

 bottom of the cask, and gradually rising till it actuates the whole mass. At tho end 

 of two or three days the manufacturer removes the fermenting materials into other 

 vessels, in order to check the process, lest putrefaction should ensue. The copper- 



