1869.] Meteorology. 549 



crystals of ice, as clistinguislied from hail, has been observed. M. 

 Silberman has himself noticed that at night thunderclouds, when 

 there is no moon, give off occasional faint coruscations from their 

 upj)er surfaces, and that when this latter appearance becomes of 

 greater perma-nency, the ordinary electric discharge, producing a 

 thunderstorm, is entirely suppressed. 



This idea of a relation between the aurora and the cirrus-cloud 

 goes to establish a relation between the aurora proper and the 

 appearance of luminous clouds, which are occasionally noticed. It 

 is also interesting in this connection to refer to the remarkable ob- 

 servations made many years ago by Sir E. Sabine, at Loch Scavaig, 

 in Skye, where he remained for a short time at anchor in a yacht. 

 One of the mountains close to the loch was constantly covered with 

 a cap of cloud, and at night discharges of a true auroral character 

 were seen to emanate from this cloud. It was distinctly proved 

 that these did not belong to an aurora at a distance, of which the 

 lower portion was obscured by the mountain. Another fact, in 

 some way corroborative of M. Silberman's views, is that some of 

 our most experienced arctic observers state that the aurora is never 

 noticed unless there be open water in the vicinity of the observer, 

 and consequently a considerable degree of humidity in the air. 



The auroras to which the papers in question especially refer are 

 very remarkable, owing to their very great extension ; that of 

 April 15 being noticed from the Azores to Central Germany, and 

 that of May 13 fi'om the British Isles to Eussia, where it was well 

 observed. In a communication to the Academy of Sciences of 

 St. Petersburg, Prof. Wild gives an extract of a letter from Von 

 Struve, of the observatory at Pulkowa, who remarked that the 

 phenomenon, though remarkably brilliant, was cliiefly noticed in 

 the east, and that the dark segment was entirely absent. This 

 latter particular was especially adverted to by M. Silberman in 

 Paris, who remarked that its place was taken by a number of small 

 clouds in various parts of the sky, forming separate auroral foci. 



The April number of the ' Proceedings of the British Meteoro- 

 logical Society' is mainly composed of two papers on the influence 

 of the moon on rainfall, which lead to diametrically opposite con- 

 clusions. Mr. Dines states, as a result of the discussion of forty 

 years' observations, that no influence is traceable ; while Mr. Glaisher 

 has submitted fifty-four years' observations to calculation, and has 

 arrived at the conclusion that the amount of rain which falls 

 increases to a maximum about the tenth day of the moon's age, 



occiu-red, tlie light of a faint aurora was perceived. Next day was very cloudy, and 

 iu places in Scotland rain fell. On the 27th the sky cleared again, another aurora 

 appeared at nightfiill ; and on tlie 2Sth a very sudden change of weather occurred, 

 the temperature falling very rapidly, while a strong N.W. wind set in, attaining 

 in some places the force of a gale. 



