XXX Presidents Address 



On September 2, 1859, just about 10.4 years ago, one of 

 the most magnificent auroras ever seen in Melbourne 

 occurred, and is, I have no doubt, well remembered by many 

 present. Large spots were visible on the sun, and at the 

 very time when we were watching the gorgeous rose coloured 

 streams shooting zenith wards, and forming their beautiful 

 corona, a strange occurrence in the sun's surface was 

 witnessed independently by two astronomers in England. 

 In the neighbourhood of one of the large spots an intensely 

 brilliant outburst of light was observed, and swept like a 

 cloud across it. It was seen for nearly five minutes, during 

 which period it was estimated to have travelled at least 

 35,000 miles. At the same time also, the earth was under a 

 violent magnetic convulsion, and grand auroras were visible 

 in both hemispheres. 



Electric currents in both the air and earth were so intense, 

 that, as Sir John Hei'schel remarked, " the telegraph wires 

 struck work." The puny force furnished by their batteries 

 was overwhelmned by the rich supplies from the fountain 

 head itself In the last aurora our wires also surrendered 

 themselves to the air currents, and for moments telegraphic 

 messages could actually be transmitted by their aid ; as a 

 rule, however, they are fitful and violent, often injuring the 

 more delicate telegraphic instruments by their great 

 intensity. 



The spectrum of auroral light has been frequently 

 observed, more especially by M. Angstrom, of XJpsala. In 

 nearly every case it has been described as consisting of two 

 lines or bands in the green part of the spectrum, near to the 

 position of the green calcium lines. During the most 

 brilliant display in April last, I was able to obtain a very 

 bright spectrum of the light with a microspectroscope. 

 Unfortunately the dispersion was small, but the light was so 

 intense as to admit of a very narrow slit. 



