AUEOKA BOREALIS. 



AUSTRALIA. 



45 



from any suitable terrestrial object white pa- 

 per, for example. As shown in the brighter 

 green patches of the sky, it remained visible 

 even when the slit was so much contracted 

 that the sodium band of a common fire would 

 have been thinned down almost to its smallest 

 breadth before extinction. At one period of 

 the display, the light was so intense that, after 

 it had been obscured a good deal by cloud, a 

 large print could have been read without much 

 difficulty. In a note upon this aurora, com- 

 municated to Nature, Prof. 0. Piazzi-Smyth 

 sums up the final mean results of a vast num- 

 ber of observations by members of the Scottish 

 Meteorological Society, and presents a numeri- 

 cal expression for each month of the year, com- 

 bining the number of times that aurora was 

 visible with the extent of country over which 

 it was observed, and the numbers stand thus : 



AUSTEALIA. At the beginning of the 

 year 1872, the area and population of the 

 British colonies in Australia were, according 

 to the latest official accounts, as follows : 



January 29.7 



February 42.5 



March 35.0 



April 27.5 



May 4.8 



June 0.0 



July 0.5 



August 12.6 



September 36.0 



October 49.4 



November 32.4 



December 28.8 



It thus appears that October and February 

 are the two months when brilliant auroras are 

 most likely to be seen, and that, of these two 

 maxima of the annual cycle, October has rather 

 the advantage. 



Prof. A. E. Twining gives to the American 

 Journal of Science the fruits of observations of 

 the aurora, made by himself and others, in differ- 

 ent parts of the United States. It is shown that 

 the maximum variation of the magnetic needle 

 in this country occurred about the time of the 

 maximum variation in England and in Ger- 

 many. Three epochs of extreme and sudden 

 deviation were noted, followed by as many of 

 sudden change back again. Prof. Twining, 

 from the data at his command, estimates the 

 height of the aurora at 352 miles above the 

 earth's surface. The ascertained height for a 

 similar zone in February, 1870, was 339 miles. 



Vogel attempts to identify the spectrum of 

 the aurora with that of the air, and submits 

 some evidence in favor of his theory. For the 

 purposes of comparison, the author determined 

 the wave-lengths of the positive lines in oxy- 

 gen, hydrogen, nitrogen, and air ; employing, 

 for the' work, Geissler tubes, the discharge 

 being that of a weak inductorium. One auroral 

 line appears to correspond with one of a system 

 of lines in the spectrum of nitrogen. The 

 lightest line in the auroral spectrum is found 

 in the spectrum of nitrogen as a faint line. 

 Another line exists both in the spectrum of 

 nitrogen, and that of air. Another line cor- 

 responds very accurately with a line in the 

 spectrum of oxygen. These, and other coin- 

 cidences, lead Vogel to conclude that the spec- 

 trum of the aurora may, with great probability, 

 be regarded as a modification of the air-spec- 

 trum, the variability of the spectra of gases, 

 under different circumstances of temperature 

 and pressure, being well established. 



The population, as given above, includes 

 859 natives in Victoria, 3,369 in South Aus- 

 tralia, and 37,502 in New Zealand. Not in- 

 cluded are the natives of Queensland and the 

 Northern Territory, whose number is estimated 

 at over 15,000. 



According to official calculations, the popu- 

 lation of Tasmania amounted in December, 

 1870, to 100,764; that of Victoria in Decem- 

 ber, 1871, to 752,287; and that of South Aus- 

 tralia, in the same month, to 189,018. 



The growth of most of the colonies has been 

 and continues to be very rapid, as may be 

 seen from the fact that Victoria, in 1836, only 

 numbered 224 ; South Australia, in 1838, 6,000, 

 and New South Wales, in 1821, 29,783 inhabi- 

 tants. In some colonies the increase of popu- 

 lation has, however, been much less marked 

 within the last ten years than before, and 

 great efforts are therefore made to give a new 

 impulse to immigration. Official investigations 

 in South Australia revealed the fact that, from 

 1861 to 1871, nearly 250,000 pounds sterling 

 had been spent by the several governments of 

 that colony in the endeavor to establish immi- 

 gration on a sound and permanent footing; 

 but that the total result thus far had been only 

 4,000 persons. The government of this colony, 

 therefore, intended to abandon the present 

 plan of paying the passage-money of the 

 immigrants, and to substitute what is known 

 as the u land order warrant" system. This 

 system is designed to encourage persons of 

 some capital to come out to the colony at their 

 own expense, receiving on arrival land orders 

 of the nominal value of 16 each. The Parlia- 

 ments of several other colonies likewise dis- 

 cussed the question of immigration, with a 

 view to making their laws on the subject 

 more effective. The Parliament of Queensland 

 restored the transferable land orders, with the 

 proviso that immigrants must reside twelve 

 months in the colony before they shall be en- 

 titled to receive their land orders, each of 

 which is to be of the value of $20, payable in 

 land, and to be at the absolute disposal of its 

 owner so soon as he shall be entitled to have 

 it issued in his favor. Employers of labor are 

 also to have a land order for each immigrant 

 whom they may introduce at their own ex- 

 pense, and assisted immigrants are to have the 

 right of receiving land orders on fulfilment of 



