Meteorology — Electricity. 179 



Giving fot- the mean of the three places, 49.86. The author considers the 

 mean temperature of the earth's surface in the vicinity of Falmouth to he 

 under 51°, and even less than 50° in a considerable portion of the mining 

 district of Corn\vall.--From Mr Fox's paper " on the Temperature of 

 Mines." Cornwall Geological Trans, vol iii. 



9. Description of the luminous arch, as seen at Perth on the 15th October. 

 — On the evening of Monday last, an electro-magnetic arch of singular 

 beauty was distinctly visible here, for more than an hour, during the 

 greater part of which it underwent little or no change of appearance. It 

 was preceded by a vivid Aurora in the north, flitting along the skirts of 

 a dark cloud, which appeared and disappeared as the coruscations of light 

 darted in irregular vertical columns along its surface. A few minutes be- 

 fore 9 o'clock a bright pencil of luminous rays began to issue from the east- 

 ern side of the horizon, exactly on the N. E. by E. | E. point, and in a 

 short time it extended itself entirely across the heavens in the form of a 

 most magnificent arch. In the mid-heaven the breadth of the arch was 

 about 4 degrees, but it contracted gradually towards each extremity, and 

 at the opposite points where it intersected the horizon, it was barely visi- 

 ble, — an appearance which was owing to the greater distance of the lower 

 parts of the arch, which must have been about 750 miles from the observer, 

 on the supposition that the portion of it over his head was 60 or 70 miles 

 above the surface of the earth. At 9 o'clock the northern edge of the arch was 

 nearly in contact with the Pleiades, which were then about 10 degrees above 

 the horizon. Passing between Mirach and Almaac, it covered near thotzenith 

 the bright star in Cygnus, and stretching onward a little to the northward 

 of Vega, it touched Ras Alhagus in Ophiuchus, after which it intersected 

 the horizon, in the S W. by W. pohit. As it cut the horizon in two points 

 which were almost diametrically opposite, it had the appearance of being 

 nearly a great arch of the celestial sphere. It did not pass, however, through 

 the zenith of Perth, but through a point which was about 7 degrees south- 

 ward from it. The axis of the arch coincided very accurately, during the 

 whole time of its appearance, with the plane of the magnetic meridian, 

 thus indicating the intimate connection between this striking phenomenon, 

 and the electro-magnetic influence. r 



10. Aurora Borealissesn at Perth on the29th October. — On Monday night, 

 between the hours of 10 and 11, the coruscations of the Aurora Borealis 

 were uncommonly vivid and changeful ; exhibiting themselves in broad 

 flashes of the most varied forms, which darted with inconceivable velocity 

 from the horizon to the zenith, and resembled rather an immense confla- 

 gration of the atmosphere, agitated by a violent tempest than the usual ap- 

 pearance of that flitting meteor. 



ELECTRICITY. 



11. Foerstemanns experiments on the conducting Power of different 

 Fluids for Voltaic Electricity. — The first column shows the specific gravity 

 of the fluid, the second the quantity of electricity which the fluid con- 



