Jaitoaet 1, 1909] 



SCIENCE 



27 



come equal to the electrostatic repulsion until 

 the charges move with the velocity of light. 

 This used to seem very puzzling to me, for I 

 reasoned as follows: Imagine a positively 

 charged hopper jSlled with steel balls, which 

 continually dropped into two p .rallel inclined 

 glass troughs. As the motion of the charged 

 balls is constantly accelerated, the electro- 

 magnetic attraction which they exert on the 

 charged balls in the other trough grows larger 

 and larger until the velocity is that of light, 

 when the streams of balls in the two troughs 

 are exerting zero force on each other (for their 

 electrostatic repulsion is then exactly balanced 

 by their electromagnetic attraction), and yet 

 they are said to be behaving like electric cur- 

 rents. Why, then, do parallel currents actu- 

 ally attract each other ? No one supposes that 

 a current in a wire travels faster than light. 

 Some years ago in Cambridge I asked Pro- 

 fessor (now Sir) J. J. Thomson about it, and 

 he replied that my analogy was all right, ex- 

 cept that according to the electron theory the 

 glass troughs should have a metal covering 

 outside, which is positively charged, the hop- 

 per should be negatively charged, and the 

 positive charge on a unit's length of a trough 

 should equal the sum of the negative charges 

 on the balls contained in that length. Then 

 the analogy, while crude, would be complete: 

 the steel balls would represent electrons, and 

 the current in the ordinary sense would flow 

 up the trough instead of down. The charge 

 on the metal covering of the trough would 

 represent the charges on the positive atoms in 

 a conductor. Under these circumstances it is 

 easy to see that attraction between the troughs 

 would ensue as soon as the balls began to 

 move. Professor Nipher's explanation, there- 

 fore, would seem to be valid only on the sup- 

 position that the positive ions in the line of 

 the disruptive discharge (which are dashing 

 towards the negative terminal) would take the 

 place of the metal-covered trough in my anal- 

 ogy, thus rendering the electromagnetic attrac- 

 tion of the moving electrons effective in draw- 

 ing them together in a column which contin- 

 ually thins out towards the positive terminal. 

 If this be true, the effect ought to be rendered 



r.-ore intense because of this consideration: 

 the analogy would then be that of the trough 

 itself (carrying a positive charge) moving in 

 the opposite direction to the motion of the 

 steel halls, thus making the relative velocity 

 of the balls greater and the attraction more 

 intense. 



But there is another way of looking at it 

 which may be more natural. The negative 

 terminal is a large sphere 10 cm. in diameter, 

 while the positive terminal is but 1 cm. in 

 diameter. The lines of force are therefore 

 strongly convergent from the negative to the 

 positive sphere, somewhat like the ropes from 

 the gas bag of a balloon to the much smaller 

 basket beneath, and electrons sliding down 

 these lines (along their negative direction, of 

 course) would naturally arrange themselves in 

 a coliunn larger at the negative end, especially 

 as these lines are themselves falling towards 

 the center line of the discharge. In this case 

 would not the phenomenon simply show the 

 pinch effect in gaseous discharge? 



Andrew H. Patterson 



Univebsitt op North Carolina, 

 December 7, 1908 



MR. MANSON's theory OP GEOLOGICAL CLIMATES 



Mr. Hanson's theory of geological climates 

 has been commended latterly in the columns 

 of Science and elsewhere, and it may be de- 

 sirable to point out why it is unsatisfactory. 



The theory as set forth in Mr. Hanson's 

 communication to the Tenth International 

 Geological Congress, in Mexico, in 1906,' is 

 briefly as follows : During Paleozoic time the 

 climate of the earth was practically uniform 

 from equator to poles, and torrid temperatures 

 were everywhere maintained by heat derived 

 from the earth and warm oceans ; the heat was 

 prevented from radiating into space and being 

 lost by a blanket of clouds surrounding the 

 whole earth. Recognizing that the heat 

 brought to the earth's surface by conduction is 

 not enough to keep up a high atmospheric 

 temperature, Mr. Manson thinks that much 

 heat was made available by the erosion of the 

 land and by hot springs, volcanic eruptions, 

 etc. Let us calculate how much heat can be 



' Proceedings, Vol. I., pp. 349-405. 



