180 Scientific Intelligence — Meteorology. 



effect of the electric current in deflecting the crystals. The crystals 

 successively deflected by electric currents would also exhibit the rush- 

 ing pencils or beams. 



It need scarcely be remarked, that differently-formed crystals 

 might give rise to different phases of the phenomenon ; while reflec- 

 tion might be combined with refraction in certain cases, especially 

 in the case of arches seen south of the anti-dip. Such an hypothesis 

 evidently assumes a source of light, independent of these optical 

 resultants, and the pulsations seen in many aurorse may be real 

 luminosities. 



It is hazardous, in the present ill-arranged state of auroral obser- 

 vation, to offer so rude a sketch of a new hypothesis, although we 

 may suffer a considerable defeat in very good company. — J. A. 

 Brourif Esq. — Proceedings of the Royal Society of Edinburgh, 

 vol. ii.. No. 39, 1850, p. 349. 



2. J. A. Broun, Esq., on the probable cause of the Diurnal Varia- 

 tion of Magnetic Variation. — It has been customary, however, to give 

 theories of the cause of magnetical variations, with reference solely 

 to the diurnal variations of the magnetic declination (and not unfre- 

 quently with a very indifferent knowledge of the facts with respect even 

 to that element.) I venture to say, that it will only be from a careful 

 comparison of the whole facts relating to the motions of a freely 

 suspended dipping-needle, not for one place, but for different and dis- 

 tant portions of the earth's surface, that a satisfactory theory will 

 be obtained. The attempt to deduce one from a consideration of the 

 declination variations alone, can only be likened to a similar attempt 

 with reference to planetary motions, the apparent position of the 

 planet being studied without any relation to the direction or rate of 

 motion of the place of observation. 



Dr Lloyd, who has done so much for magnetical science, has lately 

 brought forward a discussion of his declination observations, which he 

 considers strongly in favour of the theory that the diurnal variations 

 of magnetic declination are due to the sun's heating effect upon the 

 earth, in opposition to the atmosphere. I venture also to offer my 

 guess, founded upon a consideration of various meteorological facts, 

 that it is in the atmosphere, and not the earth, that we shall find 

 seated the secondary causes of magnetic variations. In the mean- 

 time, it is facts that are wanted.— -J". A. Broun, Esq. — Proceedings 

 of the Royal Society of Edinburgh, vol. ii.. No. 39, p. 342. 



3. Dr Faraday on the Diurnal Movements of the Magnetic 

 Needle. — The last Bakerian Lecture was delivered by Dr Faraday, 

 illustrated by experiments. After alluding to the experiments of 

 Padre Bancalari, the lecturer shewed the opposite magnetic condition 

 of oxygen and nitrogen ; the former, when enclosed in a bubble of 

 glass, is always attracted by the magnet, the latter repelled. In 

 common with iron and some other metals, oxygen loses magnetism 

 on the application of heat, and regains it again on becoming cold. 

 In this fact Dr Faraday finds the cause of the diurnal movements of 



