76 REPORT— 1902. 



a very large and anomalous temperature coefficient. E.K;periments at 

 Falmouth confirmed this and showed, moreover, the curious fact that the 

 change following a rise of temperature reversed its sign as the heating 

 continued. The instrument was dismounted and sent to Kew for ex- 

 amination in April last. Experiments made by heating the room 

 containing the apparatus confirmed those made at Falmouth as to the 

 enormous size of the appai-ent temperature coefficient ; and finding it 

 impossible to alter this appreciably, it was arranged to increase the weight 

 on the compensation bar and make some other changes. 



Even when the instrument was returned the anomalous behaviour 

 continued, and finally it was shown that by far the largest part of the 

 effect was due in some way to the method in which the mirror was 

 attached to the magnet. A change of temperature had the effect of 

 binding or twisting the mirror, and most of the eff'ect was due to this. 

 This difficulty was remedied, but the magnet has only just been returned ; 

 hence it is impossible as yet to say whether it is completely satisfactory 

 or not ; but there is every reason to suppose that this will be so. 



With regard to the special work of co-operating with the Antarctic 

 Expedition, while it was not found possible to arrange for special quick 

 views of the Falmouth instruments on the term day, Mr. Kitto under- 

 took to take such share as was possible with the existing instruments, and 

 the Secretary sent directions to him as to how this might be done. On 

 this point Mr. Kitto reports : — 



1. Care has been taken to prevent as far as possible any local dis- 

 turbance of the magnetic instruments during ' term days.' 



2. The curves for the term days have been run without interruption, 

 and hourly measurements will be made of these. 



3. The temperature has been maintained as constant as possible. 



4. The scale values have been determined with care. 



5. Absolute determinations have been taken (as far as possible) on 

 the second, fourteenth, sixteenth, and last days of each month. 



The Committee are of opinion that they should be reappointed and 

 that a further grant should be made to them for the continuance of the 

 magnetic work at Falmouth. 



The reasons for this are twofold : — (i.) It has not been found possible 

 as yet to establish the new magnetic observatory and to remove the 

 recording instruments from Kew ; at the same time the increase in 

 electrical traction to the south-west of London has caused a distinct 

 increase in the disturbances. Dr. Chree reports that the comparatively 

 quiet interludes seem fewer and the mean width of the braces larger in 

 all the elements ; thus the diurnal variation results for horizontal force 

 and declination at Falmouth in view of the disturbances near London are 

 of distinct importance until the new station has been established, (ii.) The 

 special period of magnetic research for the Antarctic lasts until March 

 1903 at least, and it is desirable to keep up the Falmouth records during 

 the whole of this period. 



In conclusion, therefore, the Committee beg leave to recommend that 

 they be reappointed, with a grant of 1001. 



