304 



ATMOSPHERIC ELECTRICITY. 



to a diameter of about one inch, and so long that it projected two inches within the 



hut and one outside. E was a round tin box which had contained a Kodak fihn, the 



lid was removed and a small brass tube, F, soldered to the bottom so that it could be 



pushed along the rod C and completely surround the end of the sulphur. G was an 



Outside i 



Inside 



• n;'-^>:-C', r-^.'-r". v-^-'^; "--■•■' ■-•'•'"' 



■■^:^'.<■^J'^;^^■:y:':^^/x^^f 





H J 



Fig. 90. Inanlator through wall. 



ordinary tin canister. The lid had a hole made in it of the size of the sulphur rod and 

 it was tacked on to the wall at H. In the bottom of the canister a small hole, just 

 larger than the rod C, was pierced ; then when the canister was pushed home into its 

 lid H it completely surrounded the whole end of the insulator and the rod C passed freely 

 into the hut. 



It will bs noticed that the tin canister was not connected with the outside and therefore 

 did not b3Com9 excessively cold, on the contrary it exposed so much of its surface to the 

 air of the hut that it quickly took the tempsrature of the air, and so water vapour was not 

 deposited on it excessively. The metal rod which connected with the outside air had the 

 inner cylinder attached to it and this tended to keep its end from remaining very cold. 

 Any moist air which entered the outer tin canister was deposited on the outside of the inner 

 tin cylinder and very little found its way within the latter to the insulator. A few pieces 

 of calcium chloride placed in the canister at J absorbed moisture and kept the air within 

 fairly dry. This insulator worked splendidly and gave practically no difficulty for several 

 months, but then the sulphur cracked and the insulation failed. When this happened a new 

 insulator on the same principle was constructed except that the rod of sulphur was replaced 

 by a rod of ebonite, and thereafter no further difficulty was experienced, so long as the sur- 

 face of the ebonite was periodically cleaned with a piece of emery paper. 



The end of the insulator outside the hut did not need the elaborate protection which 

 was necessary within the hut, so a simple tin can was placed around it to keep oil the 

 deposit of hoar frost. 



A wire was then taken in a single stretch from the end of the insulator outside the 

 hut to the collector ten yards away. During the summer months this wire was a constant 

 source of trouble, for it was continually being broken down by skua-gulls flying into it. 

 These gulls hving in a country without trees, wires or other obstructions in the free air 

 never looked where they were going when flying about the hut and not only flew into the 

 wire but on one or two occasions actually collided with the collector rod itself. It was dis- 

 tinctly annoying to lose many hours of record during fine weather owing to the clumsy 

 habits of these birds. 



