12 TRANS. OF THE ACAD. OF SCIENCE. 



stant through the day, my observations, every hour or two, 

 and always found some periodicity, though the hours of 

 maxima and minima differed somewhat. This periodicity 

 became more distinct by comparing the monthly mean of pos- 

 itive electricity at the regular hours of observation, for which 

 I refer to the tables at the end of my journal. These hours 

 I have stated there as six, nine, twelve, three, six and nine, 

 from morning to night. But the journal shows, that the ob- 

 servations were not always made exactly at these hours. 

 Not being a gentleman of leisure, I was sometimes unable to 

 make my observations at the exact time. The first observa- 

 tions in the morning, for example, show great variation in 

 time. Considering it of some importance that the first ob- 

 servations should be made before sunrise, I made my first 

 observation, on an average, about five in the summer, and 

 about seven in the winter, as the journal shows. As a mean 

 number, I stated, therefore, in the monthly tables, six o'clock 

 as the hour of first observation. On account of this irregu- 

 larity in my observations, as well as on account of the many 

 disturbing influences in our changeable climate, the hours of 

 periodicity still show some differences in the monthly table. 

 It may be, also, that these hours differ somewhat in different 

 months. But to gain the nearest approach to the law of 

 periodicity, I summed up the monthly mean at the fixed 

 hours of observation for the whole year, hoping thus to bal- 

 ance, as much as possible, all disturbing influences, and dia- 

 gram No. 3 illustrates these results. In order to ascertain, in 

 what relation tins periodicity of positive electricity stood to 

 temperature and relative humidity, I illustrated on the same 

 diagram the temperature and the relative humidity, as ob- 

 served throughout the year, at these hours. These two cor- 

 respond very accurately to each other in inverse ratio, either 

 of them forming an elliptic circle with opposite curves ; but 

 they exhibit no relation to the outlines, representing the elec- 

 trical periodicity. The only periodical phenomena, to which 

 the electrical periodicity bears resemblance, are those of the 

 barometer and of the magnetic needle. This leads me to 

 another question — to the cause or causes of atmospheric 

 electricity. 



6th. The ultimate cause of atmospheric electricity has been 

 an object of investigation for a century, and seems as yet not 

 to have been solved. Various are the conjectures and the 

 surmises in this respect ; but all of them may be classified 

 under three heads, viz: those ascribing it to cosmic, or to 

 atmospheric, or to telluric origin. Those, who ascribe atmos- 

 pheric electricity to cosmic origin, consider it as emanating 

 from that interplanetary space called the ether, from which 

 light and radiant heat flow to our globe. This somewhat 

 vague theory, not based upon physical experiment, or math- 



