396 Scientific Intelligence. 



9. Wireless Telegraphy. — It is well known that an earth con- 

 nection is used in sending messages by wireless telegraphy, both 

 in the sending and receiving apparatus. J. Val/lot and J. and 

 L. Lecarme maintain that this earth connection can be dis- 

 pensed with for long distance transmission, and certain questions 

 in regard to the part the capacity of the earth plays are thus 

 opened. Their receiving apparatus was placed in a balloon, 

 which rose to a height of 800 meters and was about 6 kilometers 

 from the sending station. — (Jomptes Rendus, cxxx, pp. 1305— 

 1307, May 14, 1900. j. t. 



10. The Spectrum of Radium. — According to the investigations 

 of Deniarcay (Compt. Rend., cxxix, p. 717, 1899) radium is a 

 new element and he gives a table of its wave lengths. C. Runge 

 has examined the spectrum and finds most of the lines which are 

 given by Demarcay in chloride of barium. The spectrum was 

 investigated in air and the preparation was also heated in vacuum 

 tubes and the spectrum showed no new lines. — Ann. der Physik, 

 No. 8, pp. 742-745, 1900. J. T. 



11. Magnetic effect of moving electrical charges. — M. Crkmieu 

 has conducted an important experiment on this subject. He has 

 endeavored to measure the inductive effect when the convective 

 current studied by Rowland is started or stopped. He could not 

 observe any such inductive effect, and therefore concludes that 

 there is no magnetic effect such as Rowland observed and that 

 the effect observed by him was not due to a moving electric 

 charge. In a criticism of Lamor's treatise on the relations 

 between ether and matter (Cambridge University Press, 1900) 

 Professor Fitzgerald remarks, that the questions raised by this 

 experiment is one of the most fundamental ones in the connection 

 between ether and matter. If M. Cremieu's experiments are sub- 

 stantiated, they will overthrow existing theories of electro-mag- 

 netism. — Nature, July 19, 1900. j. t. 



12. What electric pressure is dangerous? — In order to obtain 

 light on this much mooted question Professor H. F. Weber of 

 the Zurich Polytechnic has conducted a number of experiments 

 and reaches the following conclusions : 



A simultaneous touching of both the poles of an alternating 

 current circuit is dangerous as soon as the pressure exceeds 100 

 volts; and since it is impossible to free oneself the case must be 

 regarded as fatal whenever immediate help is not at hand. With 

 steady currents he found that all pressures between 100 and 1000 

 volts must be regarded as equally dangerous, and consequently 

 there is no reason for not using higher pressures between 500 and 

 1000 volts since they lead to more economical working of traction 

 lines. There is little danger of the public coming in contact 

 with such lines. — Nature, Aug. 23, 1900. j. t. 



