6i6 



NA TURE 



[April 27, 1905 



insidious, as there is generally little or no evidence of the 

 disease until the bark is peeled. The same remedy, that 

 of cutting out and around the diseased areas, is recom- 

 mended in both cases. 



The Transactions 0/ the Leicester Literary and Philo- 

 sophical Society (vol. ix., part i.) contain useful notes on 

 the excursions made by the several sections. The society 

 seems to have gone far afield in its studies. Thus Mr. 

 Fox Strangways conducted a highly interesting excursion 

 to Whitby, and Dr. B. Stracey contributes a sketch of 

 the igneous rocks of Morven and the Inner Hebrides. 



Mr. G. K. Gilbert has submitted to the trustees of the 

 Carnegie Institution (" Year Book " No. 3, Washington) 

 a plan for the investigation of subterranean temperature- 

 gradient by means of a deep boring in plutonic rock. It 

 is proposed that the boring be carried to a depth of 

 6000 feet, and that a site be selected in the Lithonia dis- 

 trict of Georgia. Here a fairly uniform and massive 

 granite extends about three miles in one direction and ten 

 miles in another. It is regarded as of early Palaeozoic or 

 older age. 



In an article on the pre-(j|acial v.alleys of Northumber- 

 land and Durham (Quart. Joitrn. Geol. Soc., February), Dr. 

 D. Woolacott points out that while borings have proved 

 buried valleys in the lower reaches, the higher parts of 

 the ancient valleys belong to the present drainage. The 

 Tyne and Tees were the major rivers, and the land stood 

 at a higher elevation than now. The greatest recorded 

 thickness of drift is 233 feet, and the maximum depth 

 below sea-level is 141 feet. The author discusses the 

 character of the uplift, the distribution of the drift, and its 

 subsequent erosion. 



The Nile flood in relation to the variations of atmo- 

 spheric pressure in north-east .Africa has been the sub- 

 ject of investigation by Captain H. G. Lyons, Director- 

 General .Survey Department of Egypt, and the important 

 results of the inquiry were recently communicated to the 

 Royal Society. The paper itself is too lengthy to allow 

 of even a brief abstract being made in this place, but a 

 risumi of the conclusions at which Captain Lyons has 

 arrived may be given here instead. The curve of the 

 Nile flood on the average varies inversely as the mean 

 barometric pressure of the summer months, high and low 

 pressures accompanying low and high floods respectively. 

 The pressure variations are similar over wide areas from 

 Beirut to Mauritius, and from Cairo to Hong Kong, and 

 are generally of the Indian type of curve of the Lockyers 

 or Bigelow's " direct " type. Sometimes the pressure at 

 Beirut and Cairo is in disagreement with that of the rest 

 of the area, approaching the " Cordoba " type of pressure 

 of the Lockyers or the " indirect " type of Bigelow. Con- 

 sidering monthly means of atmospheric pressure, this 

 relation is more clearly shown, and pressure above or 

 below the normal in months of the rainy season of 

 Abyssinia coincides closely with deficiency or e.xcess of 

 rainfall. From 1869 to 1903, an accurate prediction of the 

 flood from month to month could have been made in six 

 years out of seven. Using the conclusions derived from 

 the above discussion for the condition of the Nile flow 

 during the present year. Captain Lyons writes : — " With 

 weak summer rains and high pressure conditions in Sep- 

 tember and the first part of October, no large amount of 

 water can have been stored up in the soil of Abyssinia, 

 so that the springs will run off early, and a vcrv low stage 

 may be expected in 1905." 



NO. 1852, VOL. 71] 



The next meeting of the .American Institute of Mining 

 Engineers will be held at Washington in May. Special 

 attention will be devoted to the discussion of papers re- 

 lating to the genesis of ore deposits. 



The gas turbine has been regarded as the logical 

 successor of the steam turbine, and numerous devices have 

 been suggested to convert the energy of the confined pro- 

 ducts of combustion into mechanical power. In a paper 

 in the current issue of the Engineering Magazine Dr. 

 C. E. Lucke examines the thermodynamic principles in- 

 volved in such devices, and shows, as the result of experi-| 

 ments conducted at Columbia University, that this con-m 

 version is not effected by free expansion in simple nozzles:^ 

 In short, the pure gas turbine, provided with the simple 

 nozzles used by steam turbines, is a failure commercially, 

 and cannot be otherwise until some method has been found 

 to make results by free expansion more nearly equal to 

 those obtained in cylinders. 



In the Engineering and Mining Journal Mr. J. B. Jaquet 

 gives particulars of a severe explosion of rock that occurred 

 in the New Hillgrove Mine, New South Wales, on 

 December 15, 1904. The shock was felt throughout the 

 country for a mile or two around, and the area affected was 

 more than 300 feet long and 100 feet high. These sudden 

 outbursts have long been a source of anxiety to the miners 

 of Hillgrove, and there is evidence to show that they are 

 increasing in violence as greater depths are reached. 

 Explosive rocks have been described as occurring in many 

 parts of the world. In the Derbyshire lead mines, for 

 example, slickensided rocks were described by Mr. A. 

 .Strahan as being liable to burst on being scratched with 

 a pick. It has been suggested that the bursts are due to 

 molecular strain, to occluded gases, or to a compression 

 of the slates upon their being intruded by a mass of 

 granite. Mr. Jaquet believes that the Hillgrove bursts are 

 due to the walls being in a condition of strain and to the 

 fact that the slate will not bend ; it only breaks and dis- 

 integrates into a number of fragments. 



On account of their resistance to the action of sea- 

 water and of their mechanical properties when heated, a 

 number of special brasses have during the past few years 

 been applied in naval construction. In view of this, a 

 paper published by M. L. Guillet in the Bulletin de la 

 Socim d' Encouragement becomes of some general 

 interest ; it deals in detail with the changes in the 

 mechanical properties and in the microstructure of typical 

 brasses which are caused by the addition of lead, tin, 

 aluminium, and manganese. The influence of aluminium 

 is particularly noteworthy. On adding from 05 per cent, 

 to 50 per cent, of this metal to a brass containing 60 per 

 cent, of copper and 40 per cent, of zinc, a deep golden 

 colour is produced, whilst after adding more than 5 per 

 cent, of aluminium the alloy becomes superbly rose- 

 coloured. This effect is at its maximum at 7 per cent., and 

 with 10 per cent, of aluminium the colour has become a 

 silvery white. Corresp(;rding with these variations of 

 colour, striking changes in the internal structure of the 

 alloy may be traced. It may be added that aluminium 

 brasses have been applied in I'rance in the construction of 

 submarines, hut they havr imt as yet given complete 

 satisfaction. 



The March number of the Gaz:ctta contains an interest- 

 ing paper by Nicola Pappadi on the coagulation of dilute 

 solutions of silicic acid under the influence of various sub- 

 stances. Organic compounds such as glucose, saccharose, 



