abstracts: ceramic chemistry 171 



UhUCTRIC VVY.—Elecirual oscillations in antennas and inductance 

 coils. John M. Miller. Bur. Stands. Sci. Paper No. 326. Pp. 20. 

 1918. 



The mathematical theory of circuits having uniformly distributed 

 electrical characteristics, such as cables, telephone lines, and trans- 

 mission lines, is applied to the oscillations in antennas and inductance 

 coils. 



It is shown how the frequency of the natural oscillation of an anternia 

 may be determined analytically or graphically when inductance coils 

 or condensers are inserted in the lead-in. Expressions are derived 

 which permit the calculation of the effective resistance, inductance, 

 and capacity of the antenna and it is shown that in so far as frequency 

 or wave-length computations are concerned the simple formula applica- 

 ble to ordinary circuits with lumped constants gives very accurate 

 results. Experimental methods are given for determining the effec- 

 tive and static or low-frequency values of the antenna constants. 



Inductance coils are likewise treated from the standpoint of the 

 theory of distributed characteristics. Expressions are obtained for 

 the reactance of the coil at any frequency and for the natural oscilla- 

 tions of a circuit of coil and condenser. It is further shown that, in so 

 far as the frequency of oscillation is concerned, an inductance coil with 

 distributed characteristics is equivalent to a pure inductance of con- 

 stant value with a constant capacity across its terminals. Excepting 

 for skin effect, this pure inductance would be the same as the low- 

 frequency inductance of the coil. This explains a fact which has been 

 frequently observed experimentally, in particular for single layer 

 solenoids. J. M. M. 



CERAMIC CHEMIvSTRY.— 77/6' calculation of the rational analysis 

 of clays. Henry S. Washington. Journ. Amer. Ceram. Soc. 

 1:405-421. June, 1918. 



This paper discusses briefly the factors that render the so-called 

 "rational" analysis of clays uncertain, erroneous, and of little or no 

 value for any purpose. A method for calculating from the chemical 

 analysis the mineral composition, generally quartz, feldspar, and 

 kaolin, is suggested, which is an application of the principles and method 

 of calculating the "norm" of igneous rocks. In the case of clays the 

 procedure is of great simplicity and accuracy, is very expeditious after 

 the chemical analysis has been made, and yields results of great re- 

 Hability. H. S. W. 



