May 19, 1921] 



NATURE 



359 



Letters to the Editor. 



\The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



The Magnetic Storm of May 13-17. 



A TIME of unusually severe and protracted magnetic 

 'disturbance began on May 13, at about 1311. lom. 

 G.M.T., with an S.C. (•' sudden commencement"). 

 This was clearly oscillatory in D (declination), move- 

 ments to west, east, and again west following in rapid 

 succession, their extreme range being abeut 15'. 

 Within about a minute of the S.C, H (horizontal force) 

 was enhanced about 1207. The appearance of the trace 

 suggests a very rapid preliminary fall, but this is not 

 clear. Immediately after the large rise a fall began 

 in H, but the element remained above its normal 

 value for about five hours. The disturbance follow- 

 ing the S.C. was only moderate until nearly 2oh. on 

 -May 13, when considerably larger movements ap- 

 j)eared in H. Disturbance continued throughout 

 May 14, but there was a comparative lull between 

 "Sh. and i6h. Subsequent, however, to i6h. dis- 

 .turbance became very active, and the night of 

 May 14-15 was much more disturbed than the 

 previous night. 



The most disturbed period, on the whole, was 

 from oh. to 8h. on May 15. During this time 

 the D trace was off the sheet three times, but 



• only for a few minutes at a time, in the easterly 

 direction, and twice on the margin or off the sheet 

 in the westerly direction. The range actually shown 

 was 2° 12'. In the course of an hour — 4h. 25m. to 

 5h. 25m. on May 15 — movements occurred of at least 

 108' E., 107' W., 94' E., and 92' W. Few, if any, 



• of the larger D movements were absolutely uni- 

 directional. The variations in the light intensity 



; along the curve showed that superposed on the larger 

 movements were incessant short-period oscillations. 



"The H trace was similarly oscillatory, but it was 

 beyond the limits of registration in the direction of 

 H, diminishing from about 3h. to y^b. on May 15; 

 so the range shown, 6507, was doubtless much 



'exceeded. 



In vertical force the disturbance was considerable 



•on the night of May 13 between 2ih. 45m. and mid- 

 night, but on the night of May 14-15 it was enor- 

 mously greater. Assuming the scale-value to be un- 

 changed since its last determination, the range 

 reached 15007. Between 3h. 53m. and 4h. lom. on 

 May 15 there was a rise of 14007. A little later, in 

 the course of twelve minutes, there were a fall and 

 a rise each exceeding 9507. These and other large 

 movements had shorter period oscillations superposed 

 on them. The abnormally disturbed state of vertical 

 force lasted from 22h. on May 14 to 8h. on May 15. 

 During most of this time the value was much 

 depressed. 



Disturbance continued over the whole of Mav 15 

 and 16 and until the early hours of May 17. There 

 was a verv highlv disturbed time on Mav 16 between 

 2h. and loh. The H trace was off the sheet for 

 *.fullv i^ hours between 8h. and loh. C. Chree. 



Kew Observatorv, Richmond, Surrey, 

 May 17. 



NO. 2690, VOL. 107] 



The Reparation Act and the Cost of German 

 Publications. 



May I direct attention, through the columns of 

 Nature, to the serious position of scientific institu- 

 tions in this country in respect to the operation of 

 the German Reparation (Recovery) Act, 192 1? Under 

 this Act, of the cost of goods imported from Germany, 

 half is taken by the Government towards the German 

 reparation indemnity. Of course, most objects of 

 commerce imported from Germany can be made in 

 this country, and perhaps the Act is partly designed 

 to assist home industries. There are, however, certain 

 chemicals which are not at present made with suffi- 

 cient purity, but this can be corrected. 



The serious point is that there are German publica- 

 tions which in no circumstances can be conceived 

 as likely to be published in this country. The ad- 

 vance of science necessitates the study of these publi- 

 cations as soon as possible after issue. Booksellers 

 and publishers in Germany with whom I have com- 

 municated have informed me that they cannot afford 

 to sell them at less than the published price. To pay the 

 published price I have to send my cheque for actually 

 twice the published price, viz. to pay 100 per cent, 

 extra. 



I am now informed by the Board of Trade that a 

 committee " have given consideration to the question 

 of the exemption of German books and periodicals, but 

 they have not felt themselves able to make any special 

 recommendation regarding' German publications." 

 The matter seems to me to be serious, and one 

 which might be profitably considered by the scientific 

 world and the societies representing it in this country. 



J. Stanley Gardiner. 



Zoological Department, Cambridge, 

 Mav 12. 



Auroral Display. 



A DISPLAY of the aurora borealis was observed from 

 Pontypridd Common between 9.40 and 9.55 G.M.T. 

 en Friday evening. May 13, the sky being quite clear 

 of clouds. 



The chief appearance was a single band of light, 

 varying from 5° to 15° in breadth, and reaching from 

 a little below Regulus, which appeared almost central 

 in it, near the zenith, and thence to the horizon about 

 east by north, where the view was limited by a hill- 

 top with an altitude of about 15°. The band varied 

 both in width and in intensity, the middle third of its 

 length fading away and the ends alone remaining ; 

 then the middle grew bright again, the ends dis- 

 appearing ; then the full length reappeared and the 

 whole faded away evenly. The band showed no 

 colour and no flicker, only fairly rapid changes of 

 intensity ; its edges were undefined and its axis the 

 most brilliant part. It was many times more bril- 

 liant than the Milky Way, and might be compared 

 with the region of the sky round the moon as seen 

 when the latter is hidden by holding up the hand. 

 At the beginning there was a parallel band of similar 

 appearance a few degrees to the south of the eastern 

 third of the main band, and at one time when the 

 ends were disconnected they no longer appeared to 

 be in the same straight line. A. E. L. Hudson. 



The Colours of Primroses. 



Major Latham's letter (Nature. Mav 5, p. 301) 

 on the coloration of primroses has attracteid me, for 

 I have been studying the genus for several years. For 



