110 PKOCEEDIJSGS OP SECTION A. 



record of — (1) Tlie displacement of u liand spectrum under pressure; 

 (2) a displacement being directed towards the violet. This latter 

 phenomenon is shared by some lines in the ultra-violet region. 



It is at present uncertain whether the banded spectrum is due to 

 au oxide or to some molecular grouping of the atoms of silver alone. 

 Hartley, in considering his fluted flame spectrum, inclines to the latter 

 view; whicliever be the case, the spectrum at high pressures is that 

 characteristic of a molecular or compound substance, and it is in- 

 teresting to note that at the high temperature of the silver arc such a 

 spectrum can be ijroduced. The existence of banded spectra in sun 

 spots has generally been accepted as evidence tliat they are regions 

 of low temperature, but it is not out of tlie question that they are 

 areas of high temperature, and of great pressure, since the latter 

 agency seems capable of counterbalancing the tendency to dissociation 

 occasioned by the former. Whittaker pointed out, before he was 

 aware of these residts, that, from theoretical considerations based on 

 Willard Gibbs' work, this effect was to be expected. 



9.— IXTERXATIOINAL SOLAR RESEARCH. 



(Abstract of Paper presented to Section A of the Australasian Association for 

 the Advancement of Science, Brisbane Meeting, 1909.) 



By ir. GEOFFREY DUFFIELD, D.Sc. F.R.A.S. 



An account is given of the work carried on at the Mount Wilson 

 and South Kensington Solar Physics Observatories, and slides, kindly 

 supplied by Professor Hale, illustrate a portion of the equipment of 

 the Mount Wilson Observatory, and show the nature of the sun's 

 surface when photographed in the light emitted by hydrogen, calcium, 

 and iron vapours. The investigations into solar radiation, solar 

 rotation, and the spectrum and nature of svm spots are discussed, and 

 the work of the International Union for Solar Research is detailed, 

 and an account given of the steps that have been taken to secure 

 Australian co-operation in the international scheme, which is especially 

 desirable, for the following reasons : — 



(1) Australia's position in longitude is such that an Australian 



station would fill a gap at present existing in the chain 

 of observatories round the earth, and enable the sun to 

 be kept under continual observation throughout the whole 

 of the 24 hours. 



(2) Australia's position in latitude makes her co-operation 

 especially valuable, because no station devoted to solar 

 physics exists south of the equator, where one is necessary 

 to examine the question of solar radiation, and to deter- 

 mine if the fluctuations recorded by the American 

 Observatories are due to local or solar changes. 



(3) Australia's climatic conditions are uniquely favourable, 



both because her skies are clear and the simshine is 

 almost unfailing, and also because observations would be 

 possible at a time when the rainy season in India, America, 

 and Western Europe prevents observations from being 

 satisfactorily made. 



