12 



THE LAST CRUISE OF THE CARNEGIE 



Because of its relation to magnetism, a survey of terrestrial 

 electricity was added to the observational programs of the Galilee 

 and of the Carnegie. On board and ashore measurements were 

 made of the elements of atmospheric electricity. These included 

 the determination of the atmospheric potential-gradient or the 

 change in voltage with distance above the Earth's surface and of 

 conductivity or ability of the air to transport electricity. These 



MDT I 



3 4 



LOCAL MEAN TIME 

 9 10 II NOON 13 14 15 16 17 



18 19 20 21 22 23 MDT 



LOCAL MEAN TIME 

 MDT I 2 3 4 5 6 7 8 9 10 1 1 NOON 13 14 15 16 17 18 19 20 21 22 23 MDT 

 + 2501 1 1 \ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 h-/VI — /I — 1 1 1 H-250 



Hourly Values in Atmosphkric-electric Potential on Normal Day and on 



Disturbed Day 



From observations made aboard the Carnegie in the Atlantic Ocean on Cruise VII. 



two measurements give us an idea of the rate at which the Earth 

 loses its negative charge. 



But if we are to seek out the source of this charge, many other 

 factors must be observed. For example: counts of the number of 

 air-molecules carrying a charge (ions) ; measurement of the amoimt 

 of penetrating-radiation coming to the Earth from outer space 

 (since this force is capable of producing ions in the air) ; measure- 

 ment of the amount of radioactive matter in the air; and counts 

 of the so-called Aitken nuclei, or "dust-particles." 



