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297and that curve C is an accurate indication of the color-center ks = 5.4 X cm3 sec-1 concentration a t various doses. Since, however, the asand that 1 month elapsed after the irradiation (the situation sumptions and the agreement with Schulman's data are in Schulman's experiments7). It is thus implied from reasonable, it is concluded that second-order decay processes equation (19) that the activation energy for one diffusion are possible. Curve B was obtained assuming second-order jump is 0.8 to 1.1 ev. Lacking definite information on the decay processes and that the measurement was made immechanisms of the decay processes, one cannot establish mediately after the irradiation (dose rate, 300 r sec-l).The preparation of nonoriented as well as magnetically oriented specimens of 2 M e 0 . 2 B a 0 .-6Fez03 and 2Me0.3BaO. 12Fez03 is described.The M e 0 component is limited to NiO, ZnO, COO, and CuO and mixtures of these in this discussion. The orienting apparatus and technique employed are briefly described. The magnetic permeability and loss as measured at 250 M c is shown for many of these prepared compositions. The effect of the orienting magnetic field strength as well as firing temperature on the observed magnetic properties is discussed.

Apparatus is described consisting of a new type split-anode magnetron, which has been used to generate 2.5 watts of energy at 9 centimeters wavelength, with an efficiency compared to direct-current plate dissipation of 12 per cent. The methods used for measuring the tube output energy and the radiated energy are explained. Measurements of attenuation made with this apparatus up to distances of 16 miles line-of-sight through air indicate that an inverse distance law for field strength is obeyed. Modulation of the waves by means of variation in the transmission of an ionized gas is described. A summary is given of some experiments which have been made using rectifying crystals, positive grid tubes, and magnetrons as centimeter wave detectors. N THIS article a general description is given of practical apparatus for the generation and reception of centimeter waves. Data are presented with regard to the attenuation of nine-centimeter waves through the air. More detailed information with regard to separate parts of the equipment will be presented in a series of separate publications.As is well known, wavelengths as low as seventeen centimeters have been used successfully for communication across the English Channel' and continuous waves of as low as one centimeter have been produced in the laboratory by C. E. Cleeton and N. H. Williams at the University of Michigan,2 these one-centimeter waves, however, having a very small energy. It has been the aim of this development to study the production of electromagnetic waves of a length less than 10 centimeters. Since the apparatus which is used to produce the shorter waves is essentially the same as that used in the neighborhood of 10 centimeters, with the exception of a reduction in size, the results which are described here are also applicable to production of the shorter waves.

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