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KNOWLEDGE & SCIENTIFIC NEWS. 



[March, 1907. 



Lord Kelvin on Earthquakes. 



I in i;i have been for Mime lime back more than the 

 ial number and variety ol terrestrial disturbances. 

 We have had the violent earthquakes at San Francisco, 

 Chili, Kingston, and Sumatra striking terror and de- 

 solation. And we rcccntlv had one ol the most brilliant 

 i plays ol aurora borealis that have been witnessed for 

 years. At the same time there was a preponderance 

 , ii 1.11 ge spots on the sun. 



Lord Kelvin, at a meeting of the Royal Society ol 

 Edinburgh, the other day, gave his candid, learnedly 

 scientific, but not dogmatic opinion of the causes of 

 earthquakes. To do this he had to go back to the 

 formation of the earth. He returns to the atomic 

 theory derived from the Greeks of old, and popularised 

 in verse 1>\ the Latin poet, Lucretius. 



According to this theory, the primitive condition of 

 things was atomic. At first these atoms were at rest, 

 distributed uniformly in respect of average density 

 through a sphere of a thousand times the size of the 

 earth. Lucretius held that the atoms had in them the 

 inherent power of motion in parallel lines, but his 

 theory fell through when the parallel motion was trans- 

 formed into jostling and solidifying. But Lord Kelvin 

 considers that each atom would have a velocity to the 

 centre, until some came so near one another that 

 mutual molecular forces brought about combinations. 

 At that stage the density would be considerably less 

 than one-tenth of the density of water. 



When the density became so great that the atoms 

 jostled against each other, concrete matter began to be 

 formed. There would be an immense crowd of atoms 

 becoming denser round the centre, and jostling one 

 another with increasing force, until the pressure be- 

 came eased by a reactionary rebound outwards, 

 followed by several rapid alternate augmentations and 

 diminutions of the density, until ultimately molar 

 steadiness was nearly reached. This resulted in a vast 

 fluid mass at a very high temperature, which gradually 

 became lower by radiation in waves of ether in all 

 directions outward. 



There would then ensue a raising of the central 

 temperature by the increased pressure in that region, 

 caused by the shrinkage of the boundary and work 

 done due to contraction. When the temperature of 

 the central region reached its maximum and began to 

 diminish, the whole mass would go on cooling in the 

 still liquid state, till, at the surface it became frozen 

 solid. This denser material resting on the liquid 

 within would, through time, have serious changes on 

 account of the equilibrium being unstable, and large 

 portions of the crust would break away and sink in 

 the liquid. Through time this process, irregularly con- 

 tinued, would go on, until the interior, still liquid, be- 

 came blocked with masses of solid rock of all shapes 

 and sizes. This he considers to be something like the 

 state of the crust and interior of the earth at the present 

 moment. Volcanoes and earthquakes were produced 

 by the settling down of the denser solid material, and 

 the squeezing outwards of the lighter still molten rock. 

 Volcanoes might be expected to continue so long as 

 there was any molten rock in the interior, though he is 

 of opinion that solid matter constitutes much the 

 greater part of the whole mass of the earth. And, even 

 after all the molten rock has been squeezed out in the 

 forms of volcanoes, and has formed solid lava, there 

 would still be a shrinkage of the hot, solid interior, 

 which would leave cavities beneath the cool surface of 

 the earth. Earthquakes would then occur on an in- 



creasing scale of ^magnitude, as volcanoes decreased. 

 This would go on until the very central region was 



COOled— till the whole earth became solid. All this, of 



course, would depend upon there being no violent colli- 

 sion of the earth with another globe, when " the ele- 

 ments would melt with fervent heat." 



According to Lord Kelvin's theory, there can be 

 earthquakes without lava, only subsidation. The crust 

 of the earth is eool and hard, with an interior increasing 

 in temperature. Slow though it be, there is an escape 

 of heat. The interior must be shrinking more than the 

 crust. The hard outer crust would gradually be 

 dragged inward and vast cavities would be made. The 

 solid earth being- undermined in some places seemed to 

 be an explanation of earthquakes. However, alter an 

 earthquake on a large scale there would be a lowering 

 of level, or an absolute engulfing, as was the case with 

 the small island off the north-west coast of Sumatra. 

 Great sinkings of the earth are noticed after these terri- 

 ble phenomena, and, by the violent action, while some 

 part subsided, another part was tilted up. After the 

 Indian earthquake of 1897 there were very decided 

 changes of level, some parts rising up and others sink- 

 ing down. In a recent earthquake in Japan half a 

 valley was thrown down 20 feet. 



Accordingly, Lord Kelvin concluded that earthquakes 

 were due to the earth having become undermined, and 

 parts of the solid crust falling into the underground 

 cavities, thus somewhat lowering the surface level. 



J. G. Mc. P. 



Obstruction to Greenwich Observatory. 



The committee appointed to inquire into the working 

 of the County Council generating station at Green- 

 wich has recently presented its report. They recom- 

 mend : (a) The questions of vibration and obstruction 

 by chimneys to> be reviewed after two years' work with 

 the second part of the installation. (£) The second part 

 of the generating plant to be equipped with turbine 

 machinery of a perfectly balanced type, (c) When the 

 second portion is available, the reciprocating engines 

 are not to be used after 10 p.m., and shall be restricted 

 in use after 8.30 p.m. (d) The two chimneys now being 

 built not to be higher than 204 feet above O.D. (c) The 

 gases discharged not to be materially hotter than 

 250 F. (/) No further extension of the station beyond 

 the 20,000 kilowatts at present contemplated. 



The monthly meeting of the Royal Meteorological Society 

 was held on Wednesday evening, the 20th ult., at the 

 Institution of Civil Engineers, Great George Street, West- 

 minster, Dr. II. R. Mill, President, in the chair. Mr. Ed- 

 ward Mawley presented his report on the phenological 

 observations made during 1906 by observers in various parts 

 of the British Isles. The most noteworthy features of the 

 weather of the phenological year ending November, 1906, 

 as affecting vegetation, were the dry period lasting from 

 the beginning of June until the end of September and the 

 great heat and dryness of the air during the last few days 

 in August and the first few days in September. Wild plants 

 came into flower in advance of their usual dates until about 

 the middle of April, after which time they were, as a rule, 

 to about the same extent late. Such early spring immi- 

 grants as the swallow, cuckoo, and nightingale reached 

 these islands somewhat behind their average dates. The 

 only deficient farm crop, taking the country as a whole, was 

 that of hay, all the others being more or less over average. 

 The vield of apples was about average in all but the North 

 of England and in Scotland, where there was a very scanty 

 crop. Tears and plums were everywhere very deficient, 

 whereas all the small fruits yielded moderately well. As re- 

 gards the farm crops, the past year proved even a more 

 bountiful one than that of 1905. 



