OCTOBEB 28, 1910] 



SCIENCE 



605 



that the Bi-itish chart gives, m general, too 

 small dips and the German too large ones. 

 The average chart corrections for magnetic 

 horizontal intensity, disregarding sign, ap- 

 proximate 8 units of the third decimal C.G.S.; 

 the maximum correction is about 15 units for 

 either chart. For the greater part, both 

 charts give, in general, too high values. 



The observations received from the present 

 cruise down to Porto Eico, vrhich are already 

 in my oiEce, and the cable dispatch received 

 from Mr. Peters, in command of the Carnegie, 

 when he arrived at the mouth of the Amazon 

 on September 24, prove that the results of the 

 first cruise are being borne out by the present 

 one. The Carnegie left Para on the fifteenth 

 instant to continue her journey down the 

 South American coast as far as Buenos Aires, 

 from thence she will cross to Cape Town, ar- 

 riving there towards the end of March, 1911, 

 where the speaker expects to join her. The 

 present cruise will cover the Atlantic, Indian 

 and Pacific Oceans, will have an aggregate 

 length of about 65,000 miles and will termi- 

 nate at Brooklyn about July 1, 1913. 



B. Atmospheric Electricity. — Observations 

 for specific conductivity of the atmosphere, 

 with a Gerdien conductivity apparatus, and the 

 detection of the presence of radio-active ema- 

 nations, using an apparatus of the Elster and 

 Geitel type, were taken on the Carnegie by 

 Mr. Edward Kidson on the portions of the 

 cruise between Falmouth and Madeira and 

 Bermuda, and Bermuda and New York. The 

 plan was to devote alternate days to conduc- 

 tivity and radio-activity observations. This 

 program was interfered with by bad weather 

 and by the failure on some occasions of the 

 Zamboni dry pile which was used to charge 

 the collecting, wire in the radio-activity ex- 

 periments. 



From the observations obtained, no connec- 

 tion could be established between atmospheric 

 pressure, humidity, wind or cloud and the 

 conductivity. When, however, there was a 

 visible fog or haze the conductivity was greatly 

 reduced. Kain squalls of short duration did 

 not produce any effect. As the conductivity 

 is an extremely variable quantity, a very 



large number of observations is required be- 

 fore the connection with meteorological con- 

 ditions can be thoroughly investigated. One 

 effect that was noticed was that a low con- 

 ductivity was invariably obtained when the 

 vessel was in the neighborhood of land. This 

 effect was heightened in Long Island Sound 

 on the vessel's return in winter by the state 

 of the atmosphere then prevailing and prob- 

 ably by the presence of snow on the land and 

 ice on some stretches of water. 



Another noticeable fact was the persistent 

 excess of the positive conductivity over the 

 negative. The only occasions on which the re- 

 verse appeared to be consistently the case were 

 while the ship was at anchor oil' Madeira and 

 in Hamilton Harbor, Bermuda. This higher 

 value of the positive conductivity is probably 

 due chiefly to the accumulation of positive 

 ions near the negatively charged earth's sur- 

 face. If this were so, then the effect should 

 not be so noticeable in balloon observations, 

 as believed to be the case. 



None of the present theories seem sufficient 

 to explain the high degree of ionization ob- 

 served in the air. 



On December 18-19 continuous observa- 

 tions of the conductivity were taken over 

 practically twenty-four hours, in order to dis- 

 cover, if possible, a diurnal variation. The 

 day was exceedingly calm and fine, with a 

 glassy sea with a smooth, low swell. The re- 

 sults point to a higher value of the conductiv- 

 ity at night than during the day, and to an 

 almost constant value at night. This latter 

 effect is more obvious if the individual obser- 

 vations be all plotted, when the variations are 

 seen to be much greater and more irregular 

 during the day time. It would be interesting 

 to secure more of these continuous observa- 

 tions. 



The chief results of the observations for the 

 detection of radio-active matter in the atmos- 

 phere are as follows : The evidence thus far 

 gathered points to the absence of any consid- 

 erable quantity of thorium emanation in the 

 air over the ocean, however, more observations 

 are needed to decide the question definitely. 

 On several days, when the vessel was very far 



