40 PROCEEDINGS OF SECTION A. 



that the sun may be observed at one of them when observations 

 are unfavourable or impossible at the others. At present the 



stations are concentrated in three well- 

 defined areas, which are marked A, B, C 

 in the sketch, and which are separated 

 by approximately 90° of longitude. 

 The great gap between India and 

 America, at D, could be filled by an 

 Australian Observatory, whose erec- 

 tion would enable the changes in the 

 form of sun spots, their numbers and 

 areas, and the variations in the pro- 

 T, . , * *u c . minences and in the distribution of 



The circle represents the Equator. 



A— India. metallic vapours over the solar disc to 



B.— England, France, Germany, Russia, be kept Under Continual observation 



&c. ^ 



C— America (Mt. Wilson, Washington, thrOUghout the wholc of the 24 hourS. 



&c.) 

 D — Australia. 



(b) Because a Solar Observatory is required south of the Equator. 



If we neglect Mauritius, where solar work is confined to direct 

 photographs of the sun's disc, no station south of the Equator 

 contributes towards the International Scheme, though work with 

 the spectroheliograph is required in south latitudes, and that most 

 important branch of study — solar radiation — must eventually be 

 undertaken in the same part of the world. For this work a 

 fully-equipped Observatory exists at Washington, and though the 

 Smithsonian Institution has repeatedly urged the necessity of an 

 additional station in south latitudes, and has pointed out the 

 benefits that may reasonably be expected from a full study of 

 this subject, the problem is not attacked elsewhere. 



(c) Because Australia' s Climatic Conditions are uniquely favourable. 



With her almost perpetual sunshine Australia is particularly 

 suitable for this work, and, besides the promise that her clear 

 skies give of excellent photographic results, the feature that 

 makes Australian co-operation especially desirable is that obser- 

 vations would be possible in Australia at the time of year when 

 they can be least successfully made at other great Observatories — 

 Kodaikanal (India), Mt. Wilson (U.S.A.), South Kensington, &c. 

 At the first of these the rainy season lasts from November tiU 

 February, at the second from December till May, and at South 

 Kensington work is out of the question during the English winter ; 

 consequently an Observatory in Australia, where the sunshine is 

 practically unfailing from November to March, is essential for 

 supplying the solar observations for this season of the year, and 

 is necessary for the fulfilment of the scheme of international 

 co-operation. 



The comment of Sir John Eliot, K.C.I.E., F.R.S. (late 

 Astronomer and Meteorologist to the Indian Government), when 

 this was pointed out to him, was : " Sir, this Observatory is not 

 only advisable, it is essential." 



