296 



®f the restoration of the electrical equilibrium by the intervention ot 

 the frozen particles, which being imperfect conductors, become lumi- 

 nous while transmitting this electricity. In tropical and temperate 

 climates this phenomenon does not occur, because the electric equi- 

 librium is restored by means of aqueous vapours, a process which 

 often gives rise to thunder and lightning, but never to the Aurora 

 Borealis , the latter being peculiar to clear, cold and dry weather. 



8. " Theorie Balistique." Far M. Le Cornte de Predaval. Com- 

 municated by Dr. Roget, Sec. R.S. 



The author inquires into the influence which he conceives the fol- 

 lowing circumstances may have on the path of a projectile on the 

 surface of the earth; namely, first, the direction of the line of pro- 

 jection relatively to the meridian or cardinal points ; secondly, the 

 latitude of the place 5 and thirdly, the barometric conditions of the 

 atmosphere. 



9. " On the Atmospheric Tides and Meteorology of Dukhun, in the 

 East Indies." By Lieut.-Colonel W. H. Sykes, F.R.S. 



The author premises detailed descriptions of the various instru- 

 ments used in the meteorological observations recorded in this paper, 

 and of the methods employed in obtaining his results ; of which the 

 great features are the barometrical indications of diurnal and noc- 

 turnal atmospheric tides, embracing two maxima and two minima in 

 the twenty-four hours. The following are the chief topics noticed in 

 the paper, and the principal facts established by these inquiries: 

 namely, I. The removal of the doubts entertained by Humboldt, 

 founded on the authority of Horsburgh, of the suspension of the at- 

 mospheric tides during the monsoon in Western India ; the existence 

 of the four atmospheric tides already mentioned, and their occurrence 

 within the same limiting hours as in America and Europe ; the greatest 

 mean diurnal oscillations in Dukhun taking place in the coldest 

 months, and the smallest in the damp months ; whilst at Madras, 

 the smallest oscillations are in the hottest months, and in Europe it 

 is supposed that the smallest oscillations are in the coldest months. 

 2. The regular diurnal and nocturnal occurrence of the tides, 

 without a single case of interversion, whatever may be the thermo- 

 metric or hydrometric indications, or the state of the weather ; storms 

 and hurricanes only modifying, but not interrupting them. 3. The 

 anomalous fact of the mean diurnal oscillations being greater at 

 Poona, at an elevation of 1823 feet, than at the level of the sea, in a 

 lower latitude, at Madras. 4. The fact of the diurnal tides, at a 

 higher elevation than Poona, being less, whilst the nocturnal tides 

 are greater than at Poona ; and the seasons apparently not affecting 

 the limiting hours of the tides. 5. The maximum mean pressure 

 of the atmosphere being greatest in December and January; then 

 gradually diminishing until July and August ; and subsequently in- 

 creasing to the coldest months. 6. The very trifling diurnal and 

 annual oscillations compared with those of extra- tropical climates. 

 7. The annual range of the thermometer being less in Dukhun 



