ABSTRACTS OF TECHNICAL ARTICLES 229 



the magnetic field intensity are determined from ballistic galvanometer 

 deflections. While the discussion refers mainly to circular cylinders, 

 the scheme is adaptable to specimens of other shapes. It is particularly 

 designed to obtain accurate measurements of field intensity in cylinders 

 of small diameter. 



Details of a special design are given. 



Curves are given which illustrate the variation of the demagnetiza- 

 tion factor with the magnetization, as well as the dependence of this 

 relation on the material and on the dimensional ratio. 



The Use of Continued Fractions in the Design of Electrical Netivorks.^ 

 Thornton C. Fry. In U. S. Patent No. 1,570,215 and in several 

 technical papers by Bartlett and Cauer it has been shown that con- 

 tinued fractions can often be used in designing networks with pre- 

 assigned impedances. The chief difficulty of the method has been that 

 it frequently required the structures to contain negative resistances, 

 inductances or capacities and therefore the results, though correct in 

 theory, were often worthless in practice because the networks could 

 not be constructed. 



The present paper removes this difficulty in virtually all cases w^here 

 the analytic character of the desired impedance is known, that is, 

 where it can be represented by a formula and not merely by a graph. 

 In such cases the choice of a type of structure, as well as the assignment 

 of values to the elements, becomes almost a matter of routine with the 

 definite assurance in advance that no negative elements will be 

 required. 



A Voltage Regulator for Gas Discharge X-Ray Tubes} F. E. 

 Ha WORTH. This note describes a device used in connection with a gas 

 discharge x-ray tube, to regulate the voltage across it by automatically 

 adjusting a mercury valve between the tube and the pumps, thus con- 

 trolling the pressure of the gas. It has been used with tubes of the 

 Hadding and Shearer types and has operated satisfactorily for more 

 than a year. It was designed to replace the regulator described by 

 Bozorth, which is similar in principle but has certain disadvantages, 

 for example the moving parts have high inertia and adjustment is 

 required when the atmospheric pressure changes. 



The Significance of the Hydrogen Content of Charcoals/' H. H. 

 LowRY. Most studies of the thermal decomposition of hydrocarbons 



^ Am. Math. Soc. Bull., July-August, 1929. 



'" Journal of the Optical Society of America, August, 1929. 



s Journal of Physical Chemistry, September, 1929. 



