Chemistry and Physics. 351 



An intimate knowledge of the characteristics of the interrupter 

 was obtained by taking simultaneous observations on the current 

 and the potential difference by the aid of a Duddell oscillograph 

 and a falling plate camera. With a direct primary current the 

 peak value of the potential difference at the platinum point was 

 about six times the mean applied potential difference and the 

 time of the break was small compared to the make. With higher 

 frequencies not all the current was interrupted but there were no 

 oscillations so that the secondary current was unidirectional. 



With an alternating primary current, and the interrupter 

 alone in the circuit, the negative half of the wave was suppressed. 

 When the primary of an induction coil is introduced the fre- 

 quency of interruption is much greater and only a fraction of the 

 current is interrupted. When a current passes through the sec- 

 ondary spark gap the peak value of this current is great but it is 

 unidirectional. Similar observations on the old form of the 

 Wehnelt interrupter containing acid showed that the secondary 

 current there was oscillatory. 



A photograph of the curve of a secondary current through an 

 X-ray bulb when operated with the new form of interrupter 

 shows a very brief current rising to 180 milliami^eres, where the 

 mean value was only 5 milliamperes, which for ordinary uses 

 gives a satisfactory performance. — Proc. Boy. Soc. 99, 324, 1921. 



F. E. B. 



8. Within the Atom; by John Mills. Pp. XIII, 215. New 

 York, 1921 (D. Van Nostrand Company). — The purpose of the 

 author is to present to the lay reader our knowledge and current 

 theories concerning the structure of matter and the phenomena 

 of electricity. As he is himself a trained scientist and has been 

 both a college teacher and a research physicist, he speaks, if not 

 with authority, with a comprehension not possessed by the mere 

 popularizer of scientific knowledge. 



The standpoint chosen by the writer is a little unusual as he 

 neither presumes an}^ previous knowledge of electricity, 

 mechanics, or chemistry, nor does he devote any space to the 

 exposition of science in the conventional, i. e., the text-book man- 

 ner. He is even so careful lest he make the book look mathemati- 

 cal and thus inhibit the general reader that all use of formulas 

 is avoided. The usual historical order of discovery is reversed 

 and all phenomena are explained from the two postulates of the 

 electron, or negative particle of electricity, and the proton, or 

 positive particle, together with the fundamental concepts of time, 

 space and energy. The question for which an answer is sought 

 is rather ''the how" than ''the how much." Terms with 

 animistic connotation are freely used where they help us to 

 clearer thinking, though it is hard to see how "satisfaction in 

 configuration ' ' is any better than ' ' stability of equilibrium ' ' or 



