TRANSACTIONS OF SECTION A. 635- 



way, and it seems to me that the close study of the relative positions of a g^oup of 

 spots should give decisive evidence for or against the cyclone theory. 



4. If the spot is not due to cyclonic motion, is it not possible that electric 

 discharges setting out from the sun, and accelerating artificially evaporation at 

 the sun's surface, might cool those parts from which the discharge starts, and thus 

 produce a sun-spot ? The efi'ects of electric discharges on matters of solar physics 

 have already been discussed by Dr. Huggins. 



5. May not the periodicity of sun-spots, and the connection between two such 

 dissimilar phenomena as spots on the sun and magnetic disturbances on the earth, 

 be due to a periodically recurring increase in the electric conductivity of the parts 

 of space surrounding the sun ? Such an increase of conductivity might be produced 

 by meteoric matter circulating round the sun. 



6. What causes the anomalous law of rotation of the solar photosphere ? It 

 has long been known that groups of spots at the solar equator perform their revo- 

 lution in a shorter time than those in a higher latitude ; but spots are disturb- 

 ances which may have their own proper motions. Dun6r ^ has shown, however, 

 from the displacement of the Fraunhofer lines, that the whole of the layer which 

 produces these lines follows the same anomalous law, the angular velocity at a 

 latitude of 75° being 30 per cent, less than near the equator.'^ As all causes 

 acting within the sun might cause the angular velocity of the sun to be smaller 

 at the equator than at other latitudes, but could not make it greater, the only 

 explanation open to us is an outside efl'ect either by an influx of meteoric matter, 

 as suggested by Lord Kelvin, or in some other way. If we are to trust Dr. 

 Welsing's result that faculaj which have their seat below the photosphere revolve 

 in all latitudes with the same velocity, which is that of the spot velocity in the 

 equatorial region, we should have to find a cause for a retardation in higher lati- 

 tudes rather than for an acceleration at the equator. The exceptional behaviour of 

 the solar surface seems to me to deserve very careful attention from solar physicists. 

 Its explanation will probably carry with it that of many other phenomena. 



In conclusion, I should like to return for an instant to the question whether it 

 is possible by any means to render the progress of science more smooth and swift. 

 If there is any truth in the idea that two types of mind are necessary, the one cor- 

 responding to the boiler and the other to the cooler of a steam engine, it must also 

 be true that some place must be found where the two may bring their influence 

 to bear on each other. I venture to think that no better ground can be chosen 

 than that supplied by our meetings. We hear it said that the British Association 

 has fulfilled its object ; we are told that it was originally founded to create a general 

 interest in scientific problems in the towns in which it meets ; and now that popu- 

 lar lectures and popular literature are supposed to perform that work more satis- 

 factorily, we are politely asked to commit the happy despatch. There is no need 

 to go back to the original intention of those who have founded this institution, 

 whicii has at any rate adapted itself sufiiciently well to the altered circumstances 

 to maintain a beneficial influence in scientific research. 



The free discussion which takes place in our sections, the interchange of ideas 

 between men who during the rest of the year have occupied their minds, perhaps 

 too much, with some special problem, the personal intercourse between those who 

 are beginning their work with sanguine expectations, and those who have lost the 

 first freshness of their enthusiasm, should surely one and all ensure a long prosperity 

 to our meetings. If we cannot claim any longer to sow the seeds of scientific 

 interest in the towns we visit, because the interest is established, we can at any 

 rate assure those who so kindly oflTer us hospitality that they are helping power- 

 fully in the promotion of the great object which we all have at heart. 



' Oefvers. af Kongl. Vetensh. Ah. Forhandl., xlvii. 1890. 



- Although the importance of M. Duner's results would make an independent in- 

 vestigation desirable, the measurements of Mr. Crew, who by a much inferior method 

 arrived at other results, cannot have much weight as compared with those of Dun^r. 



