10 TRANS. OF THE ACAD. OF SCIENCE. 



This negative electricity was connected with and apparently 

 conditioned by the following meteorological phenomena : 



o0 times by thunder storms or hail storms; sometimes by thunder and 



lightning, without rain. 

 23 " by common rains, without thunder and lightning, but especially 



fine, drizzling rains. 

 20 " by high winds and gales, without rain, and without thunder 

 and lightning. 

 4 " by snowing. 

 1 " by fog. 



Thunder storms, as we perceive from this table, are the most 

 common cause of the change from positive into negative elec- 

 tricity. This change seems to be constant in thunder storms, 

 but the electrometer does not indicate this change many 

 hours beforehand like the barometer. True, the positive 

 electricity seems to diminish always before a storm, but the 

 negative electricity appears suddenly with the storm itself, 

 changes often in quantity during the same, and, after it, is fol- 

 lowed by perfect neutralization (0) or very weak positive 

 electricity. 



As an illustration of its action in thunder storms, I refer, 

 for instance, to March 29th, in my journal. 



Negative electricity appears generally in greater intensity 

 than positive. While the highest degree of positive electri- 

 city, that I noticed during the year, was 42°, it often happened 

 that the negative electricity during thunder storms reached 

 90°, the maximum of the electrometer. 



But not thunder storms alone create negative electricity; 

 common rains, without thunder and lightning, often produce 

 the same effect, especially fine, drizzling rains, in which the 

 condensation of vapor into water seems to go on very gra- 

 dually. 



Snowing, too, will sometimes create negative electricity, 

 especially fine snowing or sleeting ; but oftener the positive 

 electricity is by snowing increased and made more intense. 



Fog is mentioned in one instance as having produced neg- 

 ative electricity. This happened after a drizzling rain. Gen- 

 erally fog alone produces no negative electricity, but increases 

 rather the intensity of the normal positive electricity. Some 

 observers in Europe regard fog as a principal source of 

 negative electricity; but my observations, here made, give 

 quite a different result. 



Having considered the meteorological phenomena, which 

 seem to change the positive electricity of the atmosphere 

 into negative by condensation of atmospheric vapor into 

 water, it remains still to mention the dry storms as a cause 

 of negative electricity; by which term I designate high 

 winds and gales, without rain and without thunder and 

 lightning; rising suddenly in the south, or west, blowing 

 sometimes only a couple of hours, sometimes a half a day, or 



