December 2, 1915] 



NATURE 



1«3 



highest of humanitarian motives, or it may wage a 

 war of conquest on a weak neighbouring country 

 from the low motive of increasing the power of human 

 slavery as a national institution. 



From our experiences upon the earth we have 

 learned to place faith in certain simple laws ot nature, 

 amongst which are the following : — 



(i) Every particle of matter attracts every other par- 

 ticle of matter, in accordance with the law of gravita- 

 tion. 



(2) Heat always flows from a hotter body to a colder 

 body. 



(3) The volume of a given quantity of gas or vapour 

 is a function of the temperature and pressure to which 

 it is subjected. 



If a rifle, elevated at a certain angle above the level 

 surface of a lake, gives a certain muzzle velocity to the 

 bullet, the bullet will describe the curve which the 

 law of gravity says it should describe, and strike the 

 water where the law says it should strike, provided 

 we take into account two small factors that are also 

 acting — the resistance of the air and the rotation of 

 the earth. 



A red-hot cannon ball and a red-hot bullet, thrown 

 into a great bank of snow, will both cool down to 

 32° F. ; the great cannon ball slowly and the little 

 bullet rapidly. 



A rubber balloon containing a given quantity of 

 hydrogen gas can be so proportioned that if thrown 

 from a high tower on a hot summer day it will expand 

 and rise, or on a cold winter day it will contract and 

 fall. 



If a comet, a hundred million miles away, more or 

 less, is observed very accurately as to its direction 

 from us to-night, again next Monday night, and a 

 third time in two weeks from to-night, Newton's law 

 of gravitation will enable us to determine the curve 

 in which the comet is travelling around the sun, and 

 tti say where the comet may be seen three months 

 (•r six months later. 



The great stars and the small stars radiate their 

 heat energy into surrounding space : the great stars 

 cool off extremely slowly, and the small stars com- 

 paratively rapidly. Examples of this principle, it is 

 believed, are the gre;it sun, on one hand, its volume 

 1,300,000 times the earth's volume, its surface tem- 

 perature higher than 10,000° F.. and its interior tem- 

 perature immensely higher yet ; and the little earth, on 

 the other hand, cool on the surface and relatively cool 

 in the interior. 



As the great gaseous suns radiate their heat energy 

 uiicoasingly into surrounding space, they undoubtedly 

 grow slowly smaller under the force of their own 

 internal gravitation, which strives constantly to pull 

 each moh'cule of gaseous matter to the centres of the 

 stars. 



There is every reason to believe that the three 

 simple laws which we have quoted and illustrated are 

 fundamental, and operate invariably throughout the 

 stellar universe. 



.And so it is, so far as human experience has gone, 

 with all the laws of nature. 



To some people this infallible and universal 

 obedience to law — the strict accountability of effect to 

 cause — seems a hard and cruel fact and counter to 

 idealism in its various forms. This is a hasty and 

 faulty view. It is the cause-and-effect relationship 

 which gives us something dependable upon which to 

 build our civilisation. The recognition of this prin- 

 ciple, whether conscious or unconscious, is the chief 

 difference between modern civilisation and the civilisa- 

 tions which prevailed in the days of the inquisition 

 and of the Salem witchcraft. Looking at the subject 

 from the idealistic point of view, the conception 



NO. 2405, VOL. 96] 



that all matter in the universe is endowed with the 

 property of obeying law — unalterably obeying law — is 

 incomparably grander than the conception ot one law 

 prevailing here, another law prevailing there, of irre- 

 sponsible caprice operating both here and there. 



History affords no more remarkable phenomenon 

 than the retrograde movement in civilisation which 

 began with the decline of Roman power and continued 

 for more than a thousand years, approximately to the 

 epoch of the Borgias, Columbus, and Copernicus. 

 There had once existed a wonderful Greek civilisation, 

 but for twelve or fifteen centuries it was so nearly 

 suppressed as to be without serious influence upon the 

 life of the European people. Greek literature, one of 

 the world's priceless possessions, not surpassed by the 

 best modern literatures, was as complete two thousand 

 years ago as it is to-day. Yet in the Middle Ages, if 

 we except a few scatteied churchmen, it was lost to 

 the European world. A Greek science never existed. 

 Now and then, it is true, a Greek philosopher taught 

 that the earth is round, or that the earth revolves 

 around the sun, or speculated upon the constitution 

 of matter : but excepting the geometry of Euclid and 

 Archimedes, we may say that nothing was proved and 

 that no serious efforts were made to obtain proofs. 

 There could be no scientific spirit in the Greek nation 

 and civilisation as long as the Greek religion lived and 

 the Greek people and Government consulted and were 

 guided by the Greek oracles. If there had been a 

 Greek science, equal in merit with modern science, 

 think you that stupidity and superstition could have 

 secured a strangle hold upon Greek civilisation and 

 have maintained a thousand years of ignorance and 

 degradation? Intellectual life could not prosper in 

 Europe so long as dogma in Italy, only 300 years 

 ago, in the days of Bruno and Galileo, was able to 

 say, "Animals, which move, have limbs and muscles; 

 the earth has no limbs or muscles, therefore it does 

 not move " ; or so long as dogma in Massachusetts, 

 fewer than 250 years ago, was able to hang by the 

 neck until dead the woman whom it charged with 

 "giving a look toward the great meeting-house of 

 Salem, and immediately a demon entered the house 

 and tore down a part of the wainscoting." It was 

 the re-birth of science, exemplified chiefly by astro- 

 nomy, and secondarily by medicine, which gave to the 

 people of Europe the power to dispel gradually the 

 unthinkable conditions of the Middle Ages. 



Shall we try to estimate what astronomy, an ideal 

 science, sometimes called an unpractical science, has 

 done for mankind? We shall not dwell upon its so- 

 called practical applications, such as the supplying of 

 accurate time, the sailing of ships precisely to their 

 destinations on the other side of the great oceans, 

 the making of accurate maps of the continents and 

 islands, the running . of boundary lines between 

 nations, the predicting of times of high and low tides, 

 and so on ; we shall consider only the pure knowledge 

 side of the subject. 



Conceive of the earth as eternally shrouded in thick 

 clouds so that the earth's dwellers could never see 

 the sun, the moon, the stars, and the nebulae, but 

 not so thick that the sun's energy could not penetrate 

 to the soil and grow the crops. Under these condi- 

 tions, we might know the earth's rock strata to the 

 depth of a mile or two, we might know the mountains 

 and the atmosphere to a height of two or three miles, 

 we might acquire a knowledge of the oceans, but we 

 should be creatures of exceedingly narrow limits. Our 

 vision, our life, would be confined to a stratum of 

 earth and air only four or five miles in thickness. It 

 would be as if the human race went about its work 

 of raising corn for food and cotton for raiment, always 

 looking down, never looking up, knowing nothing of 



