ABSTRACT OF PHYSICAL OBSERVATIONS TAKEN 

 DURING THE PROXIMITY OF HALLEY'S COMET 

 TO THE EARTH. 



Bv Prof. William Arthur Douglas Rudge, M.A. 



The advent of Halley's Comet this year was an event looked 

 for with great interest all over the world, and in order to 

 record any unusual phenomena, it was decided to take observa- 

 tions at Grey University College, Bloemfontein, of the follow- 

 ing : — 



(i) Variation of the potential gradient in the atmosphere. 



(2) Variation of the magnetic elements. 



(3) Conductivity of the air. 



(4) Spectroscopic examination of the light from the sky. 



(5) Presence of dust in the air. 



(6) Collection and spectroscopic examination of samples 

 of air. 



(i), (2) and (3) were carried on daily for a period of three 

 weeks; one week before, and one week after the week when 

 the comet was nearest the earth. 



(4), (5) and (6) were carried on during the 17th. i8th and 

 19th of Alay. 



(i) Potential Gradient. — This was measured by a special 

 form of electroscope fixed i"2 metre above a level piece of 

 ground. The collector consisted of an aluminium wire 

 furnished with a small plate coated with a radium salt. This 

 collector proved very efficient, and has been in use for other 

 atmospheric observations for more than four months without 

 any loss of efficiency. Up to the 17th May observations were 

 taken as frequently as possible during the day, from about 

 7 a.m. to II p.m., and were continued all through the i8th 

 and 19th. From this time until the 26th they were taken as 

 time permitted. 



The general result was that a maximum potential gradient 

 occtirred at about 8 a.m. and another smaller one at about 

 6.30 p.m. The times are not very definite, as presence of 

 cloud and direction of wind, etc.. had some influence, but 

 during the period of observation the times of maxima did 

 not vary much. 



Table i shows the observations for the i8th and early morn- 

 ing of the 19th of May. The potential gradient is of course 

 proportional to the deflection. Only a few observations are 

 here recorded, but at some parts of the day they were taken 

 at intervals of one or two minutes, over 400 in all. 



Table I. 



