xlii GENERAL SUMMARY OF SCIENTIFIC AND 



undoubtedly due to the evolution of heat during the formation of 

 snow. 



Van der Mennsbrugghe shows that every disturbance in the surface 

 of a liquid gives rise to electric currents, and deduces thence the 

 conclusion that the change from invisible vapor to condensed drops 

 of fog or rain must affect the atmospheric electricity, while the orig- 

 inal evaporation of water from the ocean is a constant source of 

 electric currents ; whence he frames a comparatively simple theory 

 to account both for terrestrial electricity and atmospheric elec- 

 tricity. 



Lemstrom has developed, in the Geneva Archives, his views on the 

 nature and origin of the aurora. His theory regards this as mainly 

 a terrestrial phenomenon, due to electrical discharges through the 

 upper regions of thin air (similar to the discharges through a Geiss- 

 ler tube), and also between this air and the earth ; according to 

 him, the upper stratum of air forms a great conductor, which is near- 

 er the earth in the polar than in the equatorial regions. 



The aurora of April 7, 1874, has been elaborately investigated by 

 the author in a memoir published in the Annual Report of the Chief 

 Signal Officer of the Army. In a note on the origin of atmospheric 

 electricity. Professor Tait states that he has been making a series of 

 experiments to ascertain the part played by aqueous vapor in the 

 production of atmospheric electricity. While water is in the form 

 of vapor, it must be electrified by contact witli the gases of the at- 

 mosphere, as they are by contact with each other. He finds that the 

 precipitation of vapor in a receiver, whether produced by cold or by 

 exhaustion of the air, is always accompanied with a disengagement 

 of electricity. Further experiments with receivers of very great ca- 

 pacity are promised by Professor Tait. 



TERRESTRIAL MAGNETISM. 



No. 14 of the contributions to Terrestrial Magnetism, by General 

 Sir Edward Sabine, is published in Vol. CLXV. of the London Philo- 

 sophical Transactions. In this he presents the second half of the 

 magnetic survey of the northern hemisphere, of which the first half 

 constituted No. 13 of his contributions. These two j^apers, taken to- 

 gether with No. 12, which belongs to the southern hemisphere, em- 

 brace fully three fourths of the entire globe. In the present paper, 

 declination, inclination, and magnetic force in British units, and cor- 

 rected as far as possible to the epoch of 1842.5, are given for all 

 available stations, arranged in four zones 10 broad, from the equator 

 northward. A table is also given, comparing the observations pub- 

 lished by Sabine with the formulae and observations of Gauss and 

 Weber. 



The magnetic observations made at twelve of the stations occu- 

 pied by the Transit of Venus parties were conducted in accordance 



