386 



SCIENCE, 



[Vol. VII. , No. 169 



of refraction being plotted as ordinates and the 

 wave-lengths as abscissas, the resulting curve is 

 found to be an hyperbola. 



Prof. Alfred M. Mayer, in describing recent 

 work, stated that he had succeeded, by the use of 

 a lens of ebonite, in inflaming various substances 

 by the concentration of dark rays, for which 

 ebonite is translucent. 



Dr. S. H. Scudder gave a general account of the 

 cockroach in the past and present. Of all insect 

 types, this one is best represented in the rocks, 

 and especially the older rocks. The carboniferous, 

 especially, may fitly be called the age of cock- 

 roaches. The paleozoic cockroaches were larger, 

 the more recent smaller, than the modern. Mr. 

 G. K. Gilbert discussed the geological age of the 

 Equus fauna, maintaining that it belongs to the 

 upper quaternary (later glacial), and not to the 

 upper pliocene, where it had been assigned by 

 students of vertebrate paleontology. 



THE DATA NOW REQUISITE IN SOLAR 

 INQUIRIES. 



In order to obtain the greatest amount of assist- 

 ance from observations of the eclipsed sun, it is 

 necessary to consider in the most general way 

 the condition of solar inquiry at the time the ob- 

 servations are made. If any special work com- 

 mends itself to those interested in the problem, — 

 work which may be likely to enable us to empha- 

 size or reject existing ideas, — then that work 

 should take precedence of all other. 



Next, if the observers are sufficient in number 

 to undertake other work besides this, then that 

 work should be arranged in harmony with pre- 

 vious observations ; that is, the old methods of 

 work should be exactly followed, or they should 

 be exx>anded so that a new series of observations 

 may be begun in the light and in extension of the 

 old ones. 



In my opinion, and I only give it for what it is 

 worth, the three burning questions at the present 

 time — questions on w r hich information is required 

 in order that various forms of work may be 

 undertaken to best advantage (besides eclipse- 

 work) — are these : — 



1. The true constitution of the atmosphere of 

 the sun. By this I mean, are the various series of 

 lines of the same element observed in sun-spots, 

 e.g., limited to a certain stratum, each lower stra- 

 tum being hotter, and therefore simpler in its 

 spectrum, than the one overlying it? and do some 

 of these strata, with their special spectra, exist high 

 in the solar atmosphere, so that the Fraunhof'er 

 lines, represented in the spectrum of any one 

 substance, are the result of an integration of the 



various absorptions from the highest stratum to 

 the bottom one ? This view is sharply opposed to 

 the other, which affirms that the absorption of 

 the Fraunhofer lines is due to one unique layer 

 at the base of the atmosphere. 



I pointed out before the eclipse of 1882 that 

 crucial observations could be made during any 

 eclipse, including the time both before and after 

 totality. I made the observations : they entirely 

 supported the first view, but I do not expect 

 solar inquirers to throw overboard their own 

 views until these observations of mine are con- 

 firmed ; and I think one of the most important 

 pieces of work to be done during the next eclipse 

 is to see whether these observations can be de- 

 pended upon or not. 



One observer, I think, should repeat the work 

 over the same limited region of the spectrum, 

 near F ; another observer should be told off to 

 make similar observations in another part of the 

 spectrum. I have prepared a map of the lines 

 near E, for this purpose, showing those brigh- 

 tened on the passage from the arc to the spark, 

 and those visible alone at the temperature of the 

 oxyhydrogen flame. Whereas some of the spark 

 lines will be seen seven minutes before and after 

 totality as short, bright lines, some of the others 

 will be seen as thin, long lines just before and 

 after totality. We want to know whether the 

 lines seen at the temperature of the oxyhydrogen 

 flame will be seen at all, and, if so, to what 

 height they extend. 



2. The second point to which I attach impor- 

 tance is one which can perhaps be left to a large 

 extent to local observers, if the proper apparatus, 

 which may cost very little, be taken out. 



With this eclipse in view, I have for the last 

 several months gone over all the recorded in- 

 formation, and have discussed the photographs 

 taken at the various eclipses in connection with 

 the spots observed, especially at those times. 



The simple corona observed at a minimum with 

 a considerable equatorial extension (12 diameters, 

 according to Langley), the complex corona ob- 

 served at maximum when the spots have been 

 located at latitudes less than 20°, have driven me 

 to the view, which I shall expand on another 

 occasion, that there is a flattened ring round the 

 sun's equator, probably extending far beyond the 

 true atmosphere ; that in this ring are collected 

 the products of condensation ; and that it is from 

 the surfaces of this ring chiefly that the fall of 

 spot-forming material takes place. 



If we take any streamer in mid-latitude, we 

 find, that, while the spots may occur on the 

 equatorial side of it, none are seen on the pole- 

 ward side. I regard the streamers, therefore, like 



