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The Department of Scientific and Industrial Research has just issued, through H.M. Stationery Office, a volume of its special reports on the mineral resources of Great Britain. It deals with the geological relations, nature and uses, and mineral, chemical and physical properties of ball clays, that is to say, of those plastic "transported" clays which, when fired in an oxidising atmosphere to the temperature of certain pottery ovens approximately 1,150 deg.-1,200 deg. C.-have a white or nearly white colour. They are formed by the decomposition of felspathic rocks, by natural agencies. In this decomposition, silicates such as the felspars break down, and the products ultimately undergo hydration with the formation of the hydrated silicate of aluminium, kaolinite, and, in many cases, mixtures of hydrated oxides. Where these products are found resting in the parent rock, the clays are termed residual; where they have been transported and deposited elsewhere, they are known as transported clays. The china clays of Cornwall are typical examples of the former; the ball clays discussed in this memoir are characteristic examples of the latter. Dr. Alex Scott
Sir Courtauld Thomson, chairman of the Limmer and Trinidad Lake Asphalt Company, in his speech at the annual general meeting in March, referred to the attention the company’s staff was paying to the problem of vibration, and the writers, who have worked in collaboration with the company’s staff, are now able to reproduce some results of experiments recently carried out. W.P. Digby and R.B. Fairthorne
The preliminary report by Mott, Hay and Anderson, consulting engineers, of Westminster, to the Ministry of Transport regarding a proposed road bridge over the Forth at Queensferry has been sent to the local authorities for consideration. The report recommends that the bridge be constructed about a mile dwnstream from the railway bridge, the cost being estimated at £5,570,000 or £6,110,000, according to the route selected for the north approach. A bridge of the suspension type and having a main span of 2,400 ft. with a minimum clearance of 150 ft.-the same as the Forth Bridge-is recommended. The report states thathe present railway bridge was completed in 1889 and was located at the narrowest part of the river, advantage being taken of the rocky island of Inch-Garvie for the site of one of the main piers. It therefore occupies the best position in this stretch of the river. The bridge consists of a main span of 2,400 ft., with a minimum clearance above H.W.O.S.T. of 150 ft. This clearance is the same as that of the Forth Bridge, but while in the case of that bridge the clearance rapidly diminishes under the cantilevers, in the proposed bridge the clearance is maintained under the whole span. The side spans are each 1,040 ft. with clearance above H.W.O.S.T., diminishing from about 150 ft.