548 REPORT — 1894. 



To tills satisfactory conclusion I have only one suggestion to add. The 

 Astronomer Royal and M. Mascart now publish for the same stormy days the 

 photographic traces by which the history of a magnetic storm is mapped. la it 

 possible lor Greenwich and Paris also to agree in their choice of calm days for 

 the calculation of the diurnal variation, so that a precise similarity of method 

 may obtain not only between the English observatories, but between England and 

 France ? 



The importance of co-operation between institutions engaged on the same tasks 

 having been illustrated, I am glad to be able to announce that another step is 

 about to be taken in the same direction. For some years, in spite, I believe, of 

 great tinancial difficulties, the Cornwall Royal Polytechnic Society has maintained 

 a magnetic observatory at Falmouth. The results of the observations have hitherto 

 been printed in the Journal of the Society only, but the Royal Society has now 

 consented to publish them in the ' Proceedings.' Before long, therefore, the Kew 

 and Falmouth records, which are already worked up in the same way, will be given 

 to the world side by side. Is it too much to hope that this may be the first step 

 towards the production of a British Magnetic Year Book, in which observations 

 whose chief interest lies in their comparison may be so published as to be easily 

 compared ? 



We owe to private enterprise another advance of the same kind. The 

 managers of the new journal ' Science Progress' have made arrangements with 

 the Kew Committee for the yearly publication of a table showing the mean annual 

 values of the magnetic elements as determined at the various magnetic observa- 

 tories of the world. It will therefore in i'uture be possible to get a general idea of 

 the rate of secular change in different localities without searcliing through a 

 number of reports in different languages, which can only be consulted in the rooms 

 of the few societies or institutions to which they are annually sent. The present 

 state of our knowledge of the secular change in the magnetic elements attbrds 

 indeed very strong support to the arguments I have already adduced in favour of 

 a comparison between the instruments of our magnetic observatories. 



The whole question of tlie cause of this phenomenon has entered on a new 

 stage. It has long been recognised that the earth is not a simple magnet, but that 

 there are in each hemisphere one pole or point at which the dip needle is vertical, 

 and two foci of maximum intensity. A comparison of earlier with later magnetic 

 observations led to the conclusion that one or both of the foci in each hemisphere 

 is in motion, and that to this motion — however caused — the secular change in the 

 values of the magnetic elements is due. Thus the late Professor Balfour Stewart, 

 writing in 1883, says : ' While there is no well-established evidence to show that 

 either the pole of verticity or the centre of force to the North of America has 

 perceptibly changed its place, there is on the other hand very strong evidence to 

 show that we have a change of place on the part of the Siberian focus.' ' The i'acts 

 in favour of this conclusion are there discussed. The arguments are based, not on 

 the results of any actual observations near to the focus in question, but on the 

 behaviour of the magnet at points far distant from it in Europe and Asia. The 

 westerly march of the declination needle, which lasted in England up to 1818, 

 and the ea'^terly movement which has since replaced it, are connected with a 

 supposed easterly motion of the Siberian focus, which, it is added, ' there is some 

 reason to believe .... has recently been reversed.' In opposition, therefore, to 

 the idea of the rotation of a magnetic focus round the geographical poles which the 

 earlier magneticians adopted, Stewart seems to have regarded the motion of the 

 Siberian focus as oscillatory. 



A very different aspect is put upon the matter by a comparison of the magnetic 

 maps of the world prepared by Sabine and Creak for the epochs 1840 and ISbO 

 respectively. Captain Creak, having undertaken to report on the magnetic 

 observation-1 made during the voyage of the 'Challenger,' supplemented them with 

 the unrivalled wealth of recorded facts at the disposal of the Hydrographic Depart- 

 ment of the Admiralty. He was thus able, by a comparison with Sabine's map, to 



' Encyclopcsdia Brit., 9th edition. Art. ' Meteorology— Terrestrial Magnetism.' 



