16 



DISCOVERY 



considered as a huge solar engine, in which the waters 

 of the seas are evaporated by the heat absorbed, and 

 much of the vapour carried to high levels, at which 

 it is deposited as water, and flows down to the sea 

 By this process we get a complete cycle of operations, 

 including evaporation of water into steam, condensa- 

 tion of the steam into water, evaporation again, and 

 so on. In falling from the high level to the low level 

 of the sea, power can be obtained from this water. 

 Hydraulic power, in fact, is a form of sun-power, and 

 will continue in existence long after all the coal and 

 oil in the world have been exhausted. Coal and oil 

 have also been produced by the action of the great 

 solar engine, and they contain a portion of the energy 

 of radiation of past ages, stored up in the growing 

 wood and leaves of plants, accumulations which are 

 now being rapidly drawn upon by mankind. Coal and 

 oil are thus the result of past radiant energy, while 

 wind and water power are due to present radiant 

 energy. In one case the store in the earth is being 

 used up and cannot be replaced ; in the other case, so 

 long as the solar system lasts, power exists also." 



Approximately speaking, a total of 1,350,000 h.p. 

 could be obtained from water in the United Kingdom. 

 This total does not include the power available by 

 harnessing the Severn Channel. On this subject the 

 Board of Trade Committee in its report of December 

 1920 concluded that, " while insufficient data are 

 available to enable a definite opinion as to the economic 

 practicability of the scheme to be expressed, it merits 

 further detailed investigation. It offers a possibility 

 of an output of some 350,000 h.p. daily over a ten-hour 

 working period, corresponding to a saving of 1,270,000 

 tons of coal per annum on the basis of the consumption 

 in modern large coal-fired power stations." 



" The largest installation as yet developed in the 

 United Kingdom is the Kinlochlever Works of the 

 British Aluminium Co. Although the drainage area 

 is only 55 square mUes, the high rainfall, amounting 

 to 70 inches per annum, and the large fall of 920 feet, 

 are sufficient to give an output of about 30,000 e.h.p. 

 These works are now being increased by the addition 

 of the power to be obtained from Loch Eilde Mor. 



Of the 15,000,000 or 16,000,000 h.p. produced by 

 water-power throughout the world, " it is striking," 

 says Sir Dugald Clerk, " to find that Continental 

 Europe uses water for 27 per cent, of her total motive 

 power, and the United States 24 per cent., while the 

 United Kingdom only used o-6 per cent. Our Colonies, 

 however, use water at present for 33 per cent, of 

 their total industrial power. " 



As to the total available amount of hydraulic horse- 

 power throughout the British Empire, " Canada has 

 nearly 27,000,000 hydraulic h.p. available, and when 

 India, New Guinea, and New Zealand are added we 



attain a potential power of the order of 40,000,000 

 When we add to this the water resources of East, 

 South, and Central Africa, Egypt, Ceylon, Tasmania, 

 Australia, British Guiana, Burma, the Malay States, 

 and our own Islands, the aggregate hydraulic power of 

 the Empire approaches 70,000,000 continuous h.p. — 

 a truly remarkable power to be used in the present to a 

 small extent and in the future to a very large extent 

 as coal resources become reduced." 



WHAT IS A GOOD MEMORY ? 



" A GOOD memory should obviously be exact. An 

 experience should be recalled without the loss of any 

 characteristic details and — which is just as important — 

 without the gain of any foreign ones. Probably few 

 persons realise how common is the latter event. In 

 recounting a funny experience which has happened to 

 themselves most people are apt not only to drop the 

 unamusing details, but to trim the edges of the focal 

 events so that they dovetail perfectly into each other. 

 " Since complete recall of any experience is 

 impossible, a good memory should be serviceably 

 selective. To good remembering, as to good art, 

 leaving out the right things is indispensable. The art 

 of forgetting is but the inner aspect of the art of 

 remembering." — Prof. T. H. Pear in Remembering and 

 Forgetting. (Methuen & Co., Ltd., London., ys 6d.) 



WHERE RABBITS SPEND THE DAY 



" If you were to ask one thousand men in any town, 

 or part of the country for that matter, where rabbits 

 spend the day, nine hundred and ninety-nine of them 

 would answer : ' In burrows or holes in rocks, of course,' 

 unconscious of the fact that some rabbits never go 

 near a hole of any sort or kind unless forced there by 

 a dangerous enemy. Many rabbits that live in woods 

 sit out all day long wet or fine, and keepers profess an 

 ability to distinguish them from burrow dwellers by 

 the darker tint of the fur along their backs. 



" At certain seasons of the year burrow dwellers 

 will make a nice cosy ' seat ' in some rough tussock of 

 grass, and if left undisturbed spend the whole day in 

 it. I have watched rabbits go to their ' seats ' in the 

 early hours of the morning on many occasions, but did 

 not know until quite recently that they will sometimes 

 do so. even in the late afternoon. 



" Crossing a hill after a heavy shower of snow that 

 had fallen between two and three o'clock one day, I 

 noticed that a rabbit had left a wood immediately 

 on my right, and hopped quite leisurely, as the 

 character of its footprints indicated, out intd the 

 rough grass field through which I was passing. Expect- 

 ing to discover its returning tracks a little farther down 

 I walked on, but was disappointed. Returning to the 



