ABSTRACTS OF TECIIXICAL ARTICLES 65,3 



HCl-saturated chlorinated diphenyl containing soluble additives are in line 

 with known hydrogen-bonding tendencies of the additives. Compounds 

 which are strong organic bases do not stabilize capacitors. 



Quartz Crystals for Electrical Circuits ^ R. A. Heisikg. This book is a 

 compendium of information, both theoretical and practical, on quartz 

 crystal plates, their design and manufacture. It embodies the vast experi- 

 ence of the Bell Telephone Laboratories in research and in manufacture of 

 quartz cr}-stals. It originated from a series of lectures given by the members 

 of the Laboratories technical staff who had carried out the early studies and 

 developments in this field. By this means, engineers were trained for the 

 immense expansion in cr^'stal manufacture required to meet the demand of 

 our military forces during the War. These lectures have been reorganized 

 and rewritten, and are published together in this comprehensive book. Arti- 

 cles covering some of the various chapters have appeared in the Bell System 

 Technical Journal. 



The treatment covers in full the theory and practice of the preparation of 

 quartz crA'stals, the instruments used, including new types developed for 

 special purposes, the problems encountered in the various uses of quartz 

 cr}'stals, and the full details of the methods devised for their solution. The 

 various processing chapters, dealing with cutting and grinding, plating and 

 other topics of equal importance, include much information that appears for 

 the first time in any book. The account of the manufacturing process is 

 most complete. There are discussions of new practical methods of adjust- 

 ment to frequency, of the new performance indicator, of a new t^'pe of 

 cr>'stal cut that operates at very low frequencies, and many new develop- 

 ments that represent notable advances in crystal technology'. 



Geometrical Characterizations of Some Families of Dynamical Trajectories} 

 L. A. MacColl. The chief problem considered in this paper is that of ob- 

 taining a set of geometrical properties which shall completely characterize 

 the five-parameter family of trajectories of an electrified particle moving in 

 an arbitrary static magnetic field. A solution of the problem is found in the 

 form of a set of four principal and four subsidiar\- properties. A geometrical 

 characterization, in the form of a set of two properties, is also given of the 

 four-parameter family of trajectories of an electrified particle moving in an 

 arbitrary static magnetic field with an arbitrarily prescribed value of the 

 total energ>\ Various other properties of the families of cur\'es are dis- 

 cussed, and the paper closes w^ith a brief consideration of some analogous 

 problems in which the particle moves in a fLxed plane. 



'' Published by D. Van Nostrand Company, Inc., New York, X. Y., 1946. 

 ^ Amer. Math. Soc. Trans., July 1946. 



