president's address. 21 



to sink a shaft as deep as may 'be found practicable and at some locality 

 selected by geologists as the most likely to afford useful information. 



When we consider that the estimated cost of sinking a shaft to a 

 depth of twelve miles, at present-day prices, is not much more than 

 the cost of one day of the war to Great Britain alone, the expense 

 seems trivial as compared with the possible knowledge that might be 

 gained by an investigation into this unexplored region of the earth. It 

 might, indeed, prove of inestimable value to Science, and also throw 

 additional hght on the internal constitution of the earth in relation to 

 minerals of high specific gravity. 



In Italy, at Lardarello, bore-holes have been sunk, which dis- 

 charge large volumes of high-pressure steam, which is being utilised 

 to generate about 10,000 horse-power by turbines. At Solfatara, near 

 Naples, a similar project is on foot lo supply power to the great works 

 in the district. It seems, indeed, probable that in volcanic regions a 

 very large amount of power may be, in the future, obtained directly 

 or indirectly by boring into the earth, and that the whole subject merits 

 the most careful consideration. 



While on the subject of obtaining power, may I digress for a few 

 moments and describe an interesting phenomenon of a somewhat con- 

 verse nature — viz. that of intense pressure produced by moderate forces 

 closing up cavities in water. 



A Committee was appointed by the Admiralty in 1916 to investigate 

 the cause of the rapid erosion of the propellers of some of the ships 

 doing arduous duties. This was the first time that the problem had 

 been systematically considered. The Committee found that the 

 erosion was due to the intense blows struck upon the blades of the 

 propellers by the nuclei of vacuous cavities closing up against them. 

 Though the pressure bringing the water together was only that of the 

 atmosphere, yet it was proved that at the nucleus 20,000 atmospheres 

 might be produced. 



The phenomenon may be described as being analagous to the well- 

 known fact that nearly all the energy of the arm that swings it is con- 

 centrated in the tag of a whip. It was shown that when water flowed 

 into a conical tube which had been evacuated a pressure of over 140 tons 

 per square inch was recorded at the apex, which was capable of eroding 

 brass, steel, and in time even the hardest steel. The phenomenon may 

 occur under some conditions in rivers and waterfalls where the velocity 

 exceeds 50 feet per second, and it is probably as great a source of erosion 

 as by the washing down of boulders and pebbles. Then again, when 

 waves beat on a rocky shore, under some conditions, intense hydraulic 

 pressures will occur, quite sufficient of themselves to crush the rock 

 and to open out narrow fissures into caves. 



Research. — The whole question of the future resources of the Empire 

 1919. o 



