92 On Some Observations of Atmospheric Electricity. 



To give an idea of the extent of these indications, I may 

 state that with an electrometer where one Daniell's cell 

 will deflect five divisions, the following average readings 

 were obtained : — 



Scale reading. 



Zero 125. Raising the Conductor 18 feet ... 50 



Lowering ,, „ 250 



Moving N. to S. „ „ 150 



„ S. toN. „ „ 40 



„ E.toW. „ „ 60 



,, W. toE. „ „ 160 



I obtained some very interesting results some years ago 

 from observations made on the summit of Mount Macedon 

 while a terrific thunderstorm was passing over Melbourne 

 and the surrounding level country. 



Over the mountain it was quite clear, fine, and calm, 

 while the plains below were hidden from view by a dense 

 stratum of low-lying cloud, in and through which incessant 

 lightning could be seen, while occasionally the low and 

 distant roll of thunder could be faintly heard. 



The electrometer was placed in a tent at the bottom of 

 the tower used for trigonometrical observation, and was con- 

 nected with the collector (burning fungus) on the tower 50 

 feet high. The potential of the air was slightly positive 

 and quiet ; but simultaneous with every flash of lightning 

 the electrometer became violently but momentarily depressed 

 with negative electricity, and instantly returning to its 

 normal positive indication, suggesting the occurrence of a 

 sudden electric vacuum with each flash of lightning. 



These then are some of the most prominent facts deduced 

 from our observations of atmospheric electricity up to the 

 present time. They are interesting so far as they go, but 

 are scarcely sufficient in the present state of our knowledge 

 of the subject for tracing the relations which exist between 

 the electric condition of the earth's surface and other atmo- 

 spheric phenomena, although we may hope as our observa- 

 tions are extended (for I propose to resume them) this will 

 be eventually accomplished. Not the least interesting or 

 valuable point for investigation in this subject is the effect 

 the various electric conditions of the air have on the human 

 or animal economy, both in health and disease ; for I am 

 convinced from what I have already observed that it plays a 

 most important part in this direction, and I intend at some 

 future time to make a communication to the Society on this 

 branch of the subject. 



