452 ASTROPHYSICS 



period equal in length to the spot period? Why does the angular 

 speed of rotation increase from the poles to the equator? What is the 

 origin of the faculse and the flocculi? Why do the Fraunhofer lines 

 show little evidence of high atmospheric pressure? Why are the 

 radiations from calcium, one of the heavy elements, so prominent in 

 the higher chromospheric strata and in the prominences? A great 

 number of such questions are pressing for solution. Under the 

 stimulus of the brilliant researches of our chairman, the reinventor 

 and the leading developer of the spectroheliograph, cooperative plans 

 for solar work on a large scale are now being organized. We should 

 be vitally interested in promoting these plans; for the study of the 

 sun, as the principal foundation of astrophysical research, has been 

 unduly neglected. 



The celestial bodies develop under conditions over which we have 

 no control. We must observe the facts as they are, at long range, and 

 interpret them in accordance with those principles of physical science 

 which govern what seem to be closely related terrestrial phenomena. 

 A successful study of the development of matter in distant space, 

 under the influence of heat, pressure, electricity, and other forces of 

 nature demands a complete understanding of the action of the same 

 forces upon terrestrial matter. The astrophysicist dwells in the 

 laboratory as well as in the observatory; and laboratory researches 

 must supply the links which connect world-life and star-life. 



It has not been possible for laboratory investigators to reproduce 

 stellar phenomena on a scale approaching that occurring in nature, 

 nor to duplicate conditions of temperature and pressure existing 

 within the stars; and these are unfortunate limitations. Neverthe- 

 less, many successes have been achieved in this direction. The low- 

 temperature triumphs of Dewar, 1 Olczewski, and others approximate 

 to the conditions of space surrounding the stars. The electric arc and 

 spark appear to reproduce the temperatures of many stellar chromo- 

 spheres and reversing layers. The electric furnace of Moissan 2 seems 

 to supply temperatures comparable with those of the photosphere, 

 and it promises to throw light upon the processes of cloud formation 

 in the stars. Investigations as to the influence of va'rying pressures, 

 from almost perfect vacua up to many atmospheres, as to the 

 effects of varying electrical conditions and of other factors, 3 have 

 answered many celestial questions, and introduced others equally 

 pressing. 



Laboratory observations have established that the spectra of the 

 elements are not the same under all circumstances. We formerly 



1 Numerous papers in Proceedings of the Royal Society, principally between 

 1890 and 1900. 



2 Numerous papers in Comptes Rendus, principally between 1890 and 1900. 

 * Kayser's Handbuch der Spectroscopie, n, 289-337. 



