176 



NA TURE 



[DECEMWtR 22, 189S 



careful servant, and the salt put into it. However, after a few 

 weeks the salt became so strongly impregnated with the odour 

 of rancid grease that it was not fit to be used, and I threw it 

 away. The pot was washed a second lime w ilh scrupulous care : 

 it seemed to me (juite pure and free from odour : a new supply 

 of salt was put into it, and now for the second time the salt has 

 began to smell intolerably rancid. The interest of this is two- 

 fold. First, it shows how large an amount of impurity is able 

 to penetrate glazed porcelain, as photographers know to their 

 cost ; and secondly, it proves the possibility of concentrating 

 odour. An imperceptible discharge from the porcelain was 

 accumulated and stored in the salt until, when the lid was 

 removed, it was found to be overpoweringly strong. The scent 

 may therefore be said to have been magiiijied by these means, 

 a-s much as a sound is magnified by an ear-trumpet, or a visible 

 object Jjy a lens. F. G. 



The Twelfth Movement of the Earth. 



Under the above heading a .short article appears in the 

 Riilhlin de la Soc. Astronom. de Fiance, October 1S9S, p. 449, 

 which on account of its interest and of its brevity, as well as 

 its geological significance, is well worth citation, although the 

 matter of it has already been brought before the public by other 

 Journals and Proceedings of learned bodies. 



" The planet which we inhabit has been known by astronomers 

 to be subject to eleven ditVerent movements. 



(1) Its diurnal rotation around its axis in 23h. 56m. 



(2) Its annual revolution round the sun in 356} days. 



(3) The precession of the equinoxes in 25765 years. 



(4) The monthly movement of the earth about the centre of 

 gravity of the earth-moon couple. 



(5) The nutation caused by the attraction of the moon in iSA 

 years. 



(6) The secular variation of the obliquity of the ecliptic. 



(7) The secular variation of the eccentricity of the terrestrial 

 orbit. 



(8) The displacement of the line of apsides in 21 '000 years. 



(9) The perturbations caused by the constantly changing 

 attractions of the planets. 



(10) The displaceinent of the centre of gravity of the solar 

 system round which the earth annually turns, which centre 

 depends on the variable position of the planets. 



(11) The general translation of the solar system in the direction 

 of the constellation Hercules. 



A twelfth movement, that of the terrestrial pole to the extent 

 of I5ni. to 17m. per year, which gives rise to a slight variation of 

 latitudes for all countries, is at present the object of assiduous 

 verifications in a certain number of observatories. 



Mr. Albrecht has traced out the path followed by the 

 pole about its mean position from month to month, according to 

 the observations of latitude made since January i, 1890, to 

 June!, 1897. This slight displacement is due more especially 

 (surtout) to a variation of equilibrium produced by the move- 

 ments of the atmosphere of the ocean." 



It appears singular that this movement of the pole (and conse- 

 quent variation of latitude) thus clearly determined to be taking 

 place, has not led to any appreciations as to its possible and 

 probable significance in geology. Amongst the many causes 

 advanced to account for the derangements of land and ocean, 

 and consequent changes of climate at various geological periods, 

 has been a supposed displacement of the axis of the earth, which 

 astronomers have been unwilling to admit as having taken place 

 to any notable extent, and which up to the present it was not 

 possible to prove as having really ever existed. Sir Arch. 

 Geikie, in his "Text-book ol Geology" (1885), p. 15, discusses 

 the question sufficiently fully, and arrives at the conclusion (p. 

 17) : " Under the most favourable conditions, therefore, the 

 possible amount of deviation of the pole from its first position 

 would appear to have been too small to have seriously influenced 

 the climates of the globe within geological history." 



Secular contraction is admitted as a con.sequence of the slow 

 cooling of the earth, but the rate at which it acts, or its estima- 

 tion as a force, is hardly attainable. That it may be, and is 

 frequently a cause of earthquake action is admitted. Hence, 

 considering it as a force acting at all parts of the earth's surface 

 with greater or less energy, it is presumable that it is maximum 

 in certain places, and may be so at points in the vicinity of the 

 efjuator. Its energy may, indeed, here in places, have reached 

 the point, from time to time, of balancing the centrifugal force 



NO. I 52 I, VOL. 59] 



proper to these places ; and in this case it is evident that the 

 ground in such places might be considered as being in unstable 

 equilibrium, and liable to elevation or depression on the occur- 

 rence of very slight differences between the two forces in question 

 arising from one cause or another. Now, under such conditions 

 of equilibrium, it is just possible that a very slight variation of 

 intensity of the centrifugal force at the place considered, could 

 give rise to a derangement of the earth's surface such .as would 

 be attributed to an earthquake. This variation in the intensity 

 of the centrifugal force might be the result of the movement of 

 the polar axis, and possibly of a very slight movement such as 

 recently observed. But if it be adi.dtted that this movement is 

 continuous, and if it be suppo.sed that it may have been much 

 more intense and much more frequent in former times, it is 

 evident that it m.ay have been a potent agent in bringing about 

 alterations in the relative distribution of land and water in the 

 zone of the equator, and it is reasonable to examine the actual 

 state of this zone for some evidence of such former movement 

 of the polar axis. Now. the equatorial zone lying between 10° 

 to 15" north and south of the equator, is markedly characterised 

 by the predominance of the ocean surface. The equatorial line 

 only traversing land in Africa and South .-Vmerica, Borneo and 

 Sumatra over a total length of about 90°, the remaining 276° of 

 its extent lying on the Pacific, Atlantic and Indian Oceans. 

 The localities where it traverses the land surface are remarkable 

 in respect to their level as regards the sea. Thus the .\frican 

 part of the belt covers a large extent of the watershed valley of 

 the Congo River, and the Victoria Nyanza basin. In a quite 

 recent article in the Scientific Anuricaii Snpflcment (Sept. 24, 

 1S9S, p 19008). the basin of the Congo "has (it is said) been 

 compared by geologists to the dried up bed of an interior .sea." 

 In South .America the southern ])ortion of the zone represents 

 the watershed valley of the Amazon, that is, a low-lying tract of 

 land. The course of the zone where it traverses the Indian 

 Ocean and the islands of Borneo, Sumatra, and Celebes, is over 

 one of the most disturbed portions of the earth's surface, that is, 

 where alterations of level, with accompanying seismic and 

 volcanic phenomena, have been frequent and almost continuous. 

 Furthermore, one of the results of a change in the position of 

 the polar axis and variations of the intensities of the centrifugal 

 force on the equatorial zone would be, that for points dia- 

 metrically opposed, the decrease of centrifugal force at one 

 point would necessarily imply an increase of the force at the 

 opposite jioint, so that if subsidence took place in the one, 

 elevation should be the result in the other, so that wherever the 

 equator traverses land (representing elevation) it should be found 

 traversing ocean (or low Kind) at the oppo.site end of the diameter 

 corresponding to this elevated land surface. This practically 

 holds good, since to the African belt is antipodal, a certain ex- 

 tent of the Pacific, while to the South .American belt corre- 

 sponds diametrically the portion of the Indian Ocean occupied 

 by the islands of Sumatra, Borneo and the Celebes, so markedly 

 characterised by the evidences of former and present seismic 

 and volcanic actions. There is, therefore, some probability that 

 in the present arrangement of land and water in the equatorial 

 zone, there may be the traces of former changes of the polar 

 axis. It is well to bear in mind, as regards these small move- 

 ments of the axis frequently recurring, if not continuou.sly, and 

 giving rise consequently to small but repeated changes in the 

 relative intensities of secular contraction and centrifugal force, 

 that they may really be most potent agents of change, and that 

 therefore, however small, they acquire great significance if found 

 to be recurrent and tending to repeat themselves at more or less 

 regular intervals, and intervals much shorter than those usually 

 assigned to geological phenomena. J. P. O'kElLl v. 



The Geminid Meteors 

 Will, you allow me to supplement the observations of the 

 Geminids recorded in the first paragraph of your " .\strononiicaP 

 Column" in Natike of December 19, p. 157, by mentioning some 

 of my own ? They may be interesting as showing the continuance 

 of the shower, as I was unable to begin to keep watch until' 

 I2h. 30m. on the I2lh. Twenty-seven meteors which appeared 

 in the south and southeast were charted between that hour 

 and I4h. 45m., when clouds finally covered that part of the 

 sky. Of these, sixteen were from one or other of three radiants 

 in Gemini, the most brilliant occurring at I2h. 42ni. (= ist 

 magnitude), at I3h. 35m. (= magnitude ij), at I4h l6m. 

 (= 1st magnitude), and at I4h. l^km. ( = Jupiter in bright- 



