ABSTRACTS OF TECHNICAL ARTICLES 689 



mesh), 35.0% calcine (200 mesh). The composition of the calcine is 40.0% 

 Florida kaolin, 15.0% MgCOs, 15.0% CaCOs, 15.0% SrCO., 15.0% BaCOs, 

 calcined at 1200°C. The electrical properties of this body at 1 mc. are Q at 

 25°C, 2160; Q at 250°C, 280; Q at 350°C, 90; specific resistance at 150°C, 

 1013-5 ohm-cm. and at 300°C, 10^°'' ohm-cm. 



A Coaxial-Type Water Load and Associated Power-Measuring Apparatus.'^'' 

 R. C. Shaw and R. J. Kircher. This paper presents a description of a 

 coaxial- type water load and associated equipment suitable for measuring 

 peak pulse powers of the order of a megawatt. Water-cell loads have been 

 designed to operate at wavelengths of from 10 to 40 centimeters, where the 

 average dissipation is of the order of 3C0 watts. Ordinary tap water is used 

 in the load to dissipate the radio-frequency power. 



The Ammonia Spectrum and Line Shapes Near L25-cm Wave-Length}^ 

 Charles Hard Townes. The ammonia "inversion" lines near 1.25-cm 

 wave-length are resolved, their widths being decreased at low pressures to 

 2C0 kilocycles. Line shapes, intensities, and frequencies are measured and 

 correlated with theory. Calculated intensities and Lorentz-type broadening 

 theory fit experimental results if frequency of collision is fifteen times greater 

 than that measured by viscosity methods. Splitting due to rotation is in 

 fair agreement with a recalculation of theoretical values. A saturation efi'ect 

 is observed with increase of power absorbed per molecule and an interpreta- 

 tion made. 



Non-Uniform Transmission Lines and Reflection Coefficients}" L. R. 

 Walker and N. Wax. A first-order differential equation for the voltage 

 reflection coefi&cient of a non-uniform line is obtained and it is shown how 

 this equation may be used to calculate the resonant wave-lengths of tapered 

 lines. 



Temperature Coefficient of Ultrasonic Velocity in Solutions^ G. W. 

 WiLLARD. Extensive measurements have been made, at ten megacycles, of 

 the temperature dependence of ultrasonic velocity in liquids and liquid mix- 

 tures. All smgle liquids tested, except water, were found to have large 

 negative temperature-coefficients in the temperature range of zero to 80°C. 

 Water has a large positive coefiicient at room temperature, decreasing to 

 zero at 74°C and then becoming negative (with a peak velocity of 1557 



20 Proc. I.R.E. and Waves and Electrons, Januar>' 1947. 



" Phys. Rev., Nov. 1 and 15, 1946. 



'''^ Jour. Applied Physics, December 1946. 



'^ Jour. Acous. Soc. Amer., January 1947. 



