224 Scientific Intelligence. 



than this, it may be preferable to keep still; but Ave are then liable 

 to serious errors, should the signal happen to come from nearly in 

 front or nearly behind ; a judgment that the signal is to the 

 right or left may usually be trusted, but a judgment that it 

 comes from in front or behind is emphatically to be distrusted. 

 If, for example, the sound seems to come from a position 45° in 

 front of full right, we must be prepared for the possibility that 

 it is situated 45° behind full right. A combination of three or 

 four observers facing different ways offers advantages: a compari- 

 son of their judgments, attending only to what they think as to 

 right and left and disregarding impressions as to front and back, 

 should lead to a safe and fairly close estimate of direction." — Phil. 

 Mag., Feb. 1907, pp. 214-232. j. t. 



7. The Ionization of the Atmosphere over the Ocean. — A. S. Eve 

 of McGill University concludes as follows : 



(1) The ionization of the atmosphere over the Atlantic ocean 

 appears to be approximately the same in magnitude as in Europe 

 or North America. 



(2) The amount of radium contained in sea water is very 

 minute, and is ^-jL- to ^oV"o P art °* tne average amount deter- 

 mined by Strutt in various sedimentary and igneous rocks. 



(3) Specimens of sea water obtained, from mid-Atlantic, and a 

 sample of sea salt, indicate that a gram of sea water contains 

 about 5 X 10 -16 grams of radium. 



(4) The emanation from the radium in sea water, and the 

 penetrating radiation from the active matter contained in it, are 

 sufficient to account for the ionization observed over the ocean. 



(5) Emanation arising from radium on land, and carried to 

 sea by the wind, is the only known cause which will account for 

 the ionization effects observed over the ocean. The ionization 

 obsei'A-ed is larger than would be anticipated from such a cause, 

 but it is possible that the rate of recombination of ions over the 

 sea may be less than over the land." — Phil. Mag., Feb. 1907, pp. 

 248-258. j. T. 



8. Diurnal Periodicity of the /Spontaneous Ionization of 

 Air. — The conclusions of Alexander Wood and Norman S. 

 Campbell, working in the Cavendish Laboratory, are as follows : 



(1) The ionization in a closed vessel undergoes a permanent 

 increase for a considerable time after the gas contained in it has 

 been enclosed, but this increase depends on the nature of the 

 vessel, being comparatively large for lead vessels and tin vessels 

 and negligible for zinc vessels. 



(2) Superimposed on this variation of the ionization is a 

 periodic variation having two maxima and two minima each 

 twenty-four hours. 



(3) In their main features the curves representing this periodic 

 change are the same as the curves representing the variations of 

 atmospheric potential, and it is hoped in a later paper to establish 

 a connection between the two variations. For a possible connec- 

 tion the reader is referred to Richardson's letter to Nature 

 April 26, 1906, p. 307."— Phil Mag., Feb. 1907, pp. 265-276. 



J. T. 



