January 14, 1909 J 



NA TURE 



expeditions, since an approach towards the Pole has 

 acquired so much significance in popular estimation. An 

 examination of the present volume, however, is calculated 

 to offer a wider view with truer perspective. In it are 

 presented the results of only a portion of the physical 

 observations, those having reference to tides, pendulum 

 experiments, earthquakes, and auroral and magnetic pheno- 

 mena. Following the plan adopted in the meteorological 

 observations, the Royal Society has placed the preparation 

 of the reports on these subjects in the hands of authorities 

 most competent to deal with them. 



The tidal observations, extending from May 12, 1902, to 

 .September 20, 1003, have been discussed by Sir G. H. 

 Darwin, who remarl-is that though the tidal constants 

 derived by harmonic analysis may not be sufficiently 

 accurate to give the means of constructing a tide-table for 

 Ross Island, they arc sufficiently trustworthy to afford an 

 insight into the nature of Antarctic tides. The sum of the 

 semi-ranges of the three principal diurnal tides amounts 



who regrets that a trained physical observer did not 

 accompany the expedition, but gratefully acknowledges the 

 readiness with which Messrs. Bernacchi and Skelton 

 undertook the necessary work of mounting the instruments, 

 and the care with which they carried out the observations. 

 These observers exhibited remarkable skill and ingenuity 

 in overcoming difficultii'S connected with the apparatus, 

 and what value the observations possess is due to the 

 patience and devotion of these officers. The mean observed 

 value of gravity is slightly in excess of the theoretical, 

 and similar results have been obtained by other observers 

 in the Australian continent. There is, too, a considerable 

 discrepancy between the results obtained at the winter 

 quarters in February and in September, the explanation 

 of which it is not easy to see, as the temperature and 

 pressure were nearly the same. Mr. Bernacchi is inclined 

 to attribute this difference to the large northward move- 

 ment of ice in the Antarctic summer prior to February. 

 Dr. Chree quotes this opinion without endorsing it. 



N.iti. 



L.xpedition : View of Magnetic Ho 



, Wiiitcr Quarters. From " Physical Obser' 



to 21-6 inches, and of the three semi-diurnal tides to 

 34 inches, consequently the effect of the semi-diurnal tides 

 is scarcely noticeable on a simple inspection of the tidal 

 curves ; but a further investigation shows that the semi- 

 diurnal tide exhibits a progressive change both in ampli- 

 tude and phase as the season advances. The cause of 

 this change it is not easy to determine, since there is no 

 astronomical tide that can give an annual inequality in the 

 semi-diurnal tide of sufficient amount to account for the 

 perturbation. The tidal observations made in the Scotia 

 have been reduced by Messrs. Selby and Hunter, of the 

 National Physical Laboratory, and have been incorporated 

 in this volume. The tides in the South Orkneys, the 

 Scotia station, are normal for a place in the Southern 

 Ocean. The semi-diurnal tides are considerable, and the 

 solar tide is large in comparison with the lunar tide, the 

 ratio being 06, as against 0465 required by the equilibrium 

 theory. 



The pendulum observations, made on several occasions 

 at the winter quarters, have been discussed by Dr. Chree, 



NO. 2046, VOL. 79] 



The earthquake records discussed by Prof. Milne dis- 

 close the existence of a centre of seismic activity situated 

 to the south of New Zealand, no fewer than 1311 earth- 

 quakes having been recorded in the twenty-one months the 

 apparatus was at work. The most interesting feature in 

 the discussion has been to confirm a suspicion that Prof. 

 Milne entertained, that earthquake shocks could reappear 

 at antipodal stations without being recorded at inter- 

 mediate positions. New Zealand being nearly at our anti- 

 podes, he had noticed that many earthquakes having their 

 origin in or near that colony were registered at English 

 stations, particularly at Bidston, without disturbing the 

 instruments at observatories remote from that diameter. 

 Prof. Milne remarks that he has met with a number of 

 instances " where the movement from an epifocal area has 

 travelled round and through the world to reappear as a 

 recordable quantity at its antipodes." 



The pictures of the aurora reproduced from the draw- 

 ings of Dr. Wilson are very striking, but Mr. Bernacchi 

 remarks that though the phenomenon is frequent the dis- 



