i=;2 



NA TURE 



[June 13, 1901 



modified by Neumayer, with two needles and deflectors. 

 In all there were ninety-two observations of inclination. 

 In treating them, Mr. Steen encountered difficulties. 

 In general, the magnetic axis of a dip needle is inclined 

 to the line of geometrical symmetry, the position of which 

 is read, while the C.G. departs from the axis of rotation. 

 The former source of index error is usually eliminated 

 by reading the needle with its face alternately towards 

 and away from the face of the circle ; whilst the latter 

 source of error is removed by reversing the needle's 

 magnetisation in the middle of each experiment. The 

 needles, however, of a Fox circle are never reversed, and 

 the observer in the present case had always used the 

 needles in an invariable position. Assuming constancy 

 in the magnetisation, the error from the first source would 

 remain constant, but that from the second source would 

 vary with the inclination. The resulting error is repre- 

 sented by Mr. Steen through a formula involving three 

 unknown constants, but he finds the data insufficient for 

 determining these directly. Eventually, by having re- 

 course to some results obtained with the deflectors of the 

 Fox apparatus and to corresponding values obtained for 

 the horizontal force, and making certain assumptions, he 

 arrives at numerical results. Some doubt may, however, 

 be felt as to the measure of success attending Mr. Steen's 

 courageous efforts, and this is the more to be regretted 

 because the index correction applied averages about 50'. 

 The total intensity is dealt with on pp. 166-180. A 

 considerable number of observations had been made with 

 the Fox apparatus ; the data, however, for converting 

 these to absolute measure were not, in Mr. Steen's 

 opinion, satisfactory. Accordingly, he contents himself 

 with a list of the observational results, 



"partly for possible future utilisation, and partly, too, 

 to show what might have been done with the instrument 

 af the necessary determination of the constants had been 

 forthcoming" (p. 168). 



Mr. Steen finishes with two tables, the first, pp. 

 183-188, summarising the individual results for the 

 magnetic elements, along with the corresponding theo- 

 retical results, which Dr. Ad. Schmidt had the kindness 

 to calculate from his values of the Gaussian constants 

 for the epoch 1S85. The discrepancies, which in the rase 

 of both the horizontal force and the inclination seem 

 always of one sign, are often considerable. This may 

 be partly due to the secular change, for which no allow- 

 ance could be made. The second table arranges the 

 observational results in groups. 



VIII. Penduhtm Observations.— '^xoi. Schidtz in his 

 introduction describes the apparatus, which consisted of 

 a von Sterneck's outfit with two half-second pendulums. 

 The periods were observed at Vienna, also at Christiania 

 before and after the expedition, and Schintz concludes 

 that practically no change had occurred. During the ex- 

 pedition one observation was made on shore near the 

 Kara Sea, three on the ice, and seven inside the Fram 

 when frozen in. Particulars of each experiment are given 

 m full. The geographical coordinates of the stations 

 and the corresponding times of swing are summarised on 

 p. 55. To deduce absolute values for g, Schiotz utilises 

 the times of swing observed at Vienna and Christiania, 

 together with the absolute values found for gravity at 

 NO. 1650, VOL. 64] 



these places by von Oppolzer and himself. The values 

 thus deduced for gravity at the polar stations are com- 

 pared on p. 60 with the theoretical values given by Hel- 

 mert's formula for .^. Of the ten experiments taken on 

 board ship or on the ice, five give values above and five 

 values below the theoretical. The mean departure from 

 the theoretical values, taken irrespective of sign, amounts 

 only to three parts in 100,000 ; on the average the ob- 

 served value exceeds the theoretical by one part per 

 100,000. Schiotz believes, however, that the irregular 

 movements due to ice motion must have slightly increased 

 the observed values of g. His conclusion on p. 63 is as 

 follows : 



"The observations show that gravity may be re- 

 garded as normal over the polar basin ; and as it is not 

 probable that this is a peculiarity of the Polar Sea, we 

 are led to the assumption that gravity is normal all over 

 the great oceans. The increased attraction observed on 

 oceanic islands must, therefore, only be due to the local 

 attraction of the heaped up masses . . . that form the 

 islands." 



Prof. Schiotz seems here rather a long way from 

 his base. He devotes pp. 63-86 to drawing " some 

 conclusions respecting the constitution of the earth's 

 crust." A supplement, pp. 87-90, advances arguments 

 which, in SchicUz's opinion, justify the belief that the influ- 

 ence due to the lack of absolute rigidity in the supports 

 on the pendulums' periods was the same throughout the 

 voyage as at Christiania. 



The writers of the three memoirs have clearly acted on 

 the view that the circumstances of Nansen's polar journey 

 were so unique as to justify an unusual amount of detail in 

 recording the observations, and they have spared them- 

 selves no trouble in their anxiety to utilise the data to the 

 very utmost. A critic may perhaps, however, be pardoned 

 the doubt whether greater compression of details and 

 greater reserve in theoretical deductions might not have 

 led to a work of fully greater utility. Be this as it may, 

 the volume is to be welcomed as exceedingly opportune 

 in view of the approaching Antarctic expeditions. Those 

 responsible for the e.xercise of foresight in connection 

 with the apparatus, or the observational programmes of 

 these expeditions, would be well advised in giving its 

 contents their careful consideration. 



According to the preface of the second work mentioned 

 at the head of this notice, the Central Meteorological 

 Observatory of Japan, at Tokio, was established in 1890, 

 and "was rebuilt in July, 1897." (?) It possesses two 

 underground magnetic rooms, one for photographi- 

 cally recording, the other for eye-reading, instruments. 

 The former set of instruments are Mascart magneto- 

 graphs, the latter are said to be of a similar type. "The 

 instruments for absolute observations are illustrated in a 

 plate at the end of the volume. The declination and 

 horizontal intensity are observed with an instrument 

 due to Prof Tanakadate, possessing some unusual fea- 

 tures, of which a fuller description is given in the 

 Proc. R.S.E. for 1884-6. The times required for taking 

 the several observations are given as : declination, 

 5 minutes ; horizontal force, 20 minutes ; inclination, 

 20 minutes ! Absolute observations are taken on only 

 one day a month, but the operations are repeated 



