1 14 



SCIENTIFIC NEAVS. 



[July 1st, 1887. 



taken below through pipes to actuate the machines, just as 

 steam is taken from a boiler to an engine. There is, how- 

 ever a very important difference between steam and 

 compressed air for salt-mining purposes, for the exhaust 

 steam from an engine would condense on the salt ; and 

 above everything it is necessary to keep a salt mine dry. 

 On the other hand, the air escaping from the machines helps 

 to ventilate the mine, and keep all fresh and sweet. The 

 machines themselves are great horizontal wheels, which 

 have steel teeth, or cutters, fixed to them. These are re- 

 volved by suitable mechanism, and so cut awaj' the salt. A 

 good deal of blasting is, however, done, and the dull ex- 

 plosions reverberating through the distant galleries do not a 

 little towards adding to the strangeness of the scene. 



Those remarkable sinkings of the earth's surface to which 

 we have before referred, are not caused by salt-mining but 

 by brine-pumping. When the rock salt is mined out it is 

 necessary to provide in some way for the support of the 

 roof, but the brine-pump sucks away impartially until a vast 

 cavity is formed, and the earth sinks in to fill the hole. 

 This naturally causes a depression on the surface, and some 

 of these depressions are of remarkable extent. At Wilton, 

 not far from Northwich, there is a large pond or lake, about 

 eighty acres in extent, and in parts sixty feet deep. Not 

 very long ago, where this water now is was dry ground, 

 but the abstraction of salt from below has caused the earth 

 to settle, and the water from the river Weaver flowing in 

 has formed this large artificial, but unpremeditated pond. 

 In cases of subsidence the earth does not appear to fall in 

 with a rush, but there is a regular settlement, not rapid 

 enough, we understand, to be perceptible in its movement, 

 although the action quickly makes itself felt. 



Sheets of water caused by such subsidences, locally known 

 as " flashes," are not uncommon all down the course of the 

 Weaver. They play a useful part in helping to keep the 

 channel navigalale, for in their still water much of the sedi- 

 ment held in suspension, and brought down in flood time, 

 is deposited. In the neighbourhood of the Marston Mine 

 there is a large basin or depression by the road-side. A few 

 years ago this was high ground, but brine-pumping has 

 caused the earth to settle so that the bottom of the subsid- 

 ence is twenty to thirty feet below the ordinary level, which 

 before was an unbroken flat. There is curious evidence of 

 this in the broken track of a disused railway. In one part 

 this railway runs along the normal level of the earth's sur- 

 face. But on looking over the edge of the depression one 

 can see the continuation of the line thirty feet below, just 

 where it has been lowered by the falling of the earth. 



In the town of Northwich the buildings lean all ways with 

 most picturesque irregularity. A corner of a house may 

 fall a foot or so, windows and doors originally orthodox and 

 rectangular, become diamond-shaped, and the courses of 

 brickwork show curves that may be graceful and might be 

 pleasing enough in more appropriate situations. Then the 

 energetic Northwich householder sets to work to keep his 

 dwelling on the surface, either by "jacking up" and under- 

 filling, or in some other way. Many of the houses are 

 built on heavy beams of wood, and some are held together 

 by complete systems of iron ties, struts, and braces. If 

 matters are neglected, the householder may lose his dwell- 

 ing altogether, and there is now one house in which the 

 ground-floor has sunk so far that it has been necessary to 

 cut a new front door between what were once the windows 

 of the first floor bedroom. In other cases the bedrooms on 

 the first floor have been conveniently transformed into 

 shops on the street level. This is told of Winsford, a town 

 close by, where a great deal of brine-pumping is carried on. 

 Here the Town Hall had to be lifted eight feet in a couple 

 of years, and the church has been raised seven times. Even 



Northwich Bridge itself, which spans the river Weaver, 

 has the same downward tendency, and it is a part of the 

 regular business of the river conservators to lift the arch 

 bodily at intervals, so as to keep a sufficient height for the 

 navigation. 



Within the last year or so an effort has been made to 

 establish a salt industry on the eastern side of England, at 

 Middlesborough. The borings that have been made for 

 the purpose of finding salt have attracted much attention, 

 and success has been attained by going to considerable 

 depths. In the Cheshire district, as we have seen, there 

 are natural brine springs, and these have only to be 

 brought to the surface, but in Middlesborough the over- 

 lying strata are of an impermeable nature, and water has to 

 be taken down to the salt by tubes and pumped up again 

 in the shape of brine, as was recently described by Sir 

 Lowthian Bell at the Institution of Civil Engineers. The 

 East-Coast salt industry is yet in its infancy, and to what 

 extent it will develop remains to be seen. 



Sources of Platinum. — The most important sources 

 of platinum are the mines at Nizhne-Taglsk and Forgo- 

 Blagodat, in the Ural Mountains. About 80 per cent, 

 of the world's production comes from this source. Next 

 in importance are the gold washings of the Pinto, in 

 the United States of Colombia. About 15 per cent. 01 

 the entire product comes from this source. It is also 

 found in Brazil, Borneo, Hayti, Peru, India, Australia, 

 and in the sands of the Chaudiere River in Quebec. 

 It has recently been found in a quartz vein in New 

 Zealand. Platinum has been found in small quantities 

 in various parts of this country, associated with free 

 gold in placer deposits, but it is only from the placers of 

 California that it has been produced in a merchantable 

 quantity, which amounts to between 100 and 200 ounces 

 per annum, and is sold at 75 cents per troy ounce. It 

 contains about 85 per cent, of the metal, and is shipped to 

 London to be refined. The platinum used in this country 

 comes almost entirely from Russia, and the imports amount 

 to between 2,000 and 3,000 pounds annually. 



Platinum "ore," as it is called, contains iridium, 

 rhodium, gold, copper, and iron. It is sometimes, though 

 seldom, found crystallized in cubes and octahedrons, but 

 more usually in rounded or flattened grains, or " sand," 

 having a metallic lustre. The importers' price for refined 

 platinum has risen steadily since 1883, when it was 6 dols. 

 50 cents to 7 dols. 50 cents per ounce, according to the 

 quantity bought. It is now worth 7 dols. 50 cents to 8 dols. 

 50 cents. The principal consumption is in the manufacture 

 of chemical apparatus, but within the past few years the 

 use of incandescent electric lights, and also gas jets made 

 luminous by a bested platinum spiral, have caused an 

 increased demand for the metal, and the steady rise in 

 price during the past three years may be referred to this 

 cause. — Georgetown Courier. 



The Royal Society. — At the Annual Meeting of the 

 Royal Society for the election of Fellows, held at the 

 Society's rooms in Burlington House on Thursday last, the 

 following gentlemen were elected : — John Young Buchanan, 

 M.A., John Theodore Cash, M.D., Sir James Nicholas 

 Douglass, M.I.C.E., Prof. James Alfred Ewing, B.Sc, Prof. 

 George Forbes, M.A., William Richard Gowers, M.D., Prof. 

 Alexander B. W. Kennedy, M.I.C.E., George King, M.B., 

 Sir John Kirk, M.D., Prof. Oliver Joseph Lodge, D.Sc, 

 Prof. John Milne, F.G.S., Rev. Octavius Pickard-Cambridge, 

 M.A., George James Snelus, F.C.S., Thomas, Lord Walsing 

 ham, and William Whitaker, B.A. 



