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Theoretical estimates of the neutron production in the Columbia University shock tube, for a shock speed of 100 cm/Msec, predicted about 4x 10 5 neutrons. Four 1B85 thyrode Geiger tubes, wrapped in 10-mil silver sheet and covered with a polyethylene moderator, were placed about the 50-cm point on the shock tube. For slightly slower shock speeds than shown in Table I no neutrons were observed. However, for the shock speeds indicated in Table I, neutrons have been detected, and by using a Los Alamos calibration 7 for this detector, we estimate a yield of about 5xl0 5 neutrons. However, the close agreement between predictions and this measurement is thought to be more fortuitous than an indication of accuracy. A pilot B scintillator, shielded by 1 in. of lead, detected a burst of radiation which may be neutrons or nonthermal hard x rays. We do not know yet whether the neutrons are truly of thermonuclear origin.The experimental data indicate that the shockcreated plasma volume of ~10 4 cm 3 has an internal energy density (nkT) of about 1.2 J/cm 3 , a macroscopic kinetic energy (IpF 2 ) of about 2.8 J/cm 3 , and that about 20% of the energy originally stored in the high-voltage capacitor bank was transferred into the plasma in the first halfcycle of the current pulse.We acknowledge the many contributions by Dr. B. Miller in the design and early develop-Almost all previous optical studies of cholesteric liquid-crystal films were made on systems composed of cholesterol-derived molecules. The optical properties of these films were qualitatively explained by assuming a distribution in orientation of Bragg scattering domains embedded in a matrix of constant refractive index. 1 Adams and co-workers have shown that, among other difficulties, inhomogeneity in Bragg spacing makes it impractical to measure this angular ment of the shock tube, and thank Mr. M. Cea,