87 



assured that contemporaneous observations would throw 

 much light upon the subject. 



. ^ The more important results obtained by Mr. Clarke dur- 

 ing the past two months are : 



1st. That atmospheric electricity in serene weather is 

 invariably positive. 



Snd. That it is more intense during fogs, especially if 

 they occur during frosty weather. 



3rd. That in cloudy weather, (without rain,) the aerial 

 electricity diminishes in intensity. 



4th. That during heavy rain, hail, snow, or sleet, (and 

 particularly at their commencement,) the atmospheric elec- 

 tricity is very intense. This electricity is, at first, invariably 

 negative, but sometimes changes its state frequently during 

 the storm. 



5th. That the periods of its diurnal changes of intensity 

 vary considerably, the intensity being at a maximum (during 

 the past two months) each day some time between 7J, a. m., 

 and 10 J, A. M. ; becoming almost evanescent at noon ; and as- 

 cending progressively for a few hours previous to sun-set. 

 It acquires its nocturnal maximum some time between 9 and 

 12, p. M. ; when it again declines gradually until some hours 

 after sun-rise. 



6th. That the nocturnal electricity, with or without dew, 

 is stronger than the diurnal. 



The foregoing observations are for the most part con- 

 firmed by those of Cavallo. But, the sixth observation does 

 not agree with those of Canton, Abbe Mazeas, M. De 

 Saussure, and Mr, Cross ; the two former observers not 

 having observed any electricity at night, and the two latter 

 finding it weaker than by day. M. De Saussure conceived 

 the electricity of the evening to be strong in consequence of 

 the dew acting as a conductor, whilst the author has ob- 

 served it very strong when there was no dew. M. De Saus- 

 sure has likewise stated the maximum of diurnal electricity 



