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2. The improper integral defined as the limit of a sum. We first consider the case where ak = 1 (k =1, 2, 3, * * * ). A fundamental difficulty not encountered in the previous paper is apparent from the definition of .fof(x)dx. Bromwich and Hardy have considered this problem [2]. As they point out, the ordinary definition of this improper integral is by means of a double (repeated) limit; and in order to replace this limit by the single limit

NASA and the Max Planck Institute for Extraterrestrial Physics (MPE), Munich, Germany, conducted a cooperative experiment involving the release and study of a barium cloud at 31,500 km altitude near the equatorial plane. The release was made near local magnetic midnight on Sept. 21, 1971. The MPE-built spacecraft contained a canister of 16 kg of Ba CuO mixture, a two-axis magnetometer, and other payload instrumentation. The objectives of the experiment were to investigate the interaction of the ionized barium cloud with the ambient medium and to deduce the properties of electric fields in the proximity of the release. An overview of the project is given to briefly summarize the organization, responsibilities, objectives, instrumentation, and operational aspects of the project.

If excited, the free oscillations of the moon can be recorded by a long-period seismograph, gravimeter, or tiltmeter placed on the lunar surface, andthe gross aspects of the moon’s internal structure can be deduced by comparing observed frequencies of vibration with those predicted theoretically for various assumed lunar models. Low order oscillations involve the body as a whole, and the higher order oscillations depend principally on the physical properties of the body at successively shallower depths. Numerical calculations for the spheroidal and torsional oscillations are discussed for several assumed lunar models and demonstrate the sensitivity of the periods of vibration to variations in assumed internal structure. Torsional vibrations involve shear type motions only; spheroidal vibrations involve radial displacements also and disturb the gravitational field. The rate at which the amplitudes of oscillation decay with time will allow important inferences to be made concerning the elastic or inelastic behaviour of the material inside the moon. The higher order free oscillations may be regarded as dispersive surface waves, and ob-servations of surface wave trains by a long-period seismograph will allow a separation to be made between plausible internal lunar structures. Because of the simplicity of the observations, passive seismic experiments should rank high in priority for future exploration of the moon and planets.

Sudden, repetitive illumination of the dark-adapted monkey eye produces transient changes in the electroretinogram and transocular potential which can last an hour or longer.