428 



JV.^ rURE 



[March 3, 1887 



phorescence spectrum given by a mixture of 6i parts yttrium 

 and 39 parts of samarium, and illustrated it by a coloured 

 lithograph. Also in a paper read before the Royal Society, 

 February 25, 18S6 (Roy. Soc. Proc. vol. xl. p. 236), I described 

 .ind figured the pliosphorescent spectrum of an earth olitaincd in 



the fractionation of yttria which was identical, chemically and 

 spectroscopically, with an earth discovered by M. de Marignac, 

 and provisionally called by him Yo. I repeat here these spectra, 

 and the spectrum of yttrium added for comparison. Omitting 

 minor details, it is seen that the \' a spectnim is identical with 



'that of the mixture yttrium 61, samarium 39, with one important 

 e.xception— the citron line of GS in the former spectrum is absent 

 •in the latter. Could I by any means remove G5 from tlie mixture 

 of yttrium and samarium the residue would be Ya. I have little 

 doubt that this will soon be accomplished, but in the meantime 

 the phosphoroscope enables us to remove the line of G5 frotn the 



mixture. It is only necessary to add strontium to a suitable 

 mixture of yitrium and samarium and view the phosphorescing 

 mixture in the instrument when the wheel is rotating rapidly, to 

 obtain a spectrum which is indistinguishable from that of Ya. 



{ To be continued. ) 



PRE-SCIENTIFIC THEORIES OF THE CA USES 



OF EARTHQ UAKES 

 TN the course of a lecture delivered recently before the Rigaku 



Kyokai, or Science Society of Tokio, on the causes of earth- 

 quakes. Prof. Milne classified the theories as to the cause of these 

 phenomena into three kinds — unscientific, ^«aj/-scientific, and 

 scientific. In the former class he included the explanations of 

 the Negro preachers at Charleston after the late earthquakes 

 there, that they occurred in consequence of the wickedness of 

 the population. The Mussulmans in Java recently prayed to the 

 volcanoes there to cease their shakings, at the same time pro- 

 mising reformation of life. That earthquakes are the direct 

 result of man's wickedness is an idea that has always been 

 common. ."Vbout 1750 earthquakes were felt in many parts of 

 Europe, which were widely attributed to this cause, and in- 

 numerable sermons were preached inculcating the lesson that if 

 mankind would live better lives there would be no more earth- 

 quakes. In 1786, after a shock at Palermo, the people are 

 recorded to have gone about scourging themselves, and looking 

 extremely humble and penitent. An English poem called "The 

 Earthquake," published in 1750, alleged, in somewhat halting 

 verse, that the disturbances were not due to an unknown force, 

 nor to the groanings of the imprisoned vapours, nor yet to the 

 shaking of the shores with fabled Tridents : — 



" Ah no ! the tread of impious feet 



The conscious earth impatient bears 

 And shuddering with the guilty weight. 



One common grave for her bad race prepares." 

 From this theory, which can scarcely have satisfied the poet 

 himself, Prof. Milne passed on to the myths which attribute 

 earthquakes to a creature living underground. In Japan it is an 

 "earthquake-insect " covered with scales, andhaving eight legs, 

 or a great fish having a certain rock on his head which helped to 

 l<eep him quiet. In Mongolia the animal was said to be a fro-^, in 



India the world-bearing elephant, in the Celebes a world-support- 

 ing hog, in North America a tortoise. In Siberia there was a 

 myth, connected with the great bones found there, that these were 

 the remains of animals that lived underground, the trampling 

 of which made the ground shake. In Kamchatka the legend 

 was connected with a god, Tuil, who went out hunting with his 

 dogs. When these latter stopped to scratch themselves, their 

 movements produced earthquakes. In Scandinavian mythology, 

 Loki, having killed his brother Baldwin, was bound to a rock 

 face upwards, so that the poison of a serpent should drop on his 

 face. Loki's wife, however, intercepted the poison in a vessel, 

 and it was only when she had to go away to empty the dish that a 

 fev/ drops reached him and caused him to writhe and shake the 

 earth. The lecturer had no means of collecting the fables 

 of the southern hemisphere ; but they would obviously be 

 worth knowing for purposes of comparison. As to quasi- 

 scientific theoiies, these endeavoured to account for earth- 

 quakes as p.irts of the ordinary operations of Nature. It 

 was supposed, for instance, that they were produced by the 

 action of wind confined inside the earth. The Chinese philo- 

 sophers said that Yang, the male element, entered the earth and 

 caused it to expand, and to shake the ground in its efforts to 

 escape. Its effects would be more violent beneath the mountains 

 than in the plains, and therefore earthquakes in the north of 

 China, which was mountainous, were said to be more violent than 

 those in the south. It was supposed that when the wind was blow- 

 ing strongly on the surface of the earth, there was calm beneath, 

 and 7'ice versa. Aristotle and many other classical writers attri- 

 buted earthquakes to wind in the earth. Shakespeare, in 

 " Henry IV.," speaks of the teeming earth being pinched and 

 vexed with a kind of colic by the imprisoning of unruly wind 

 within her womb. Then came the theory of electrical discharges, 

 which was advocated in 1760 by Dr. Stukely, as well as by 

 Percival and Priestley. They are strongly held in California at 

 the present day, where it was believed that the network of rails 



