REPORT OF COMMITTEE ON OBSERVATORIES 1 63 



Might I quote from a letter to me from Mr. Evershed on this 

 subject. He writes : 



' ' We are apt to become too f amiHar with sun spots to be sur- 

 prised at their occurrence ; but I am sure that when their origin 

 and meaning is really understood, a key will be found to a great 

 many other solar and stellar problems. I consider that as a prelim- 

 inarj^ the spot spectrum should be investigated with a bolometer in 

 the visible region and infra-red to find out whether the discrepancy 

 between thermal and visual estimates of spot darkness is real, and, 

 if so, where in the spectrum is the excess of radiation measured 

 thermally. 



"Another point to clear up is the resolution of parts of the spot 

 band into lines observed by Young and Duner. Does this apply to 

 all spots and to all parts of the spectrum, and is the emission spec- 

 trum of the photosphere itself really continuous under high disper- 

 sion ? 



' ' It seems to me that until the fundamental radiation of spots is 

 satisfactorily cleared up the study of widened lines is of secondary 

 importance." 



The other subject to which my attention has been directed is the 

 study of Jupiter, It seems to me that that planet ought not to 

 be left to the scrutiny of amateurs, but should be systematically 

 observed at some permanent and endowed obser\'atory. As the sun 

 is the only hot star which we can study in detail, Jupiter is the only 

 cold star, and we are fortunate in having representatives of both 

 ends of the series within our reach. In my connection with the 

 British Astronomical Association, my attention has been drawn to 

 the special field for work which this planet offers. The Association 

 has done what it could in the matter. Its object was the training 

 of amateur obser\'ers, and their direction to real systematic pur- 

 poseful work in place of the desultory star gazing which is too often 

 all that amateurs achieve. So far it has been most successful, and 

 the Jupiter Section numbers quite half a dozen observers of the very 

 first rank, beside others who may in course of time attain the same 

 skill. But an association such as ours can never be a substitute for 

 a permanent observ^atory. A very large proportion of its efforts 

 must be spent in the work of training ; there is no guarantee that 

 any of its observers will be able to follow up a research for a long- 

 continued period, and the means for the proper discussion of obser- 

 vations are quite lacking. I might mention, as an example, one of 

 our most active students of Jupiter, Capt. P. B, Molesworth, R. E., 

 of Ceylon. He has been working there for nearly eight j'ears, and 

 in a single apparition has obtained nearly 4,000 transits of spots 



