A variable-length vacuum-insulated liquid hydrogen transfer line is described. The vacuum system is semi-permanent, and segments of the line are assembled with only threaded vacuum fittings. Thermal stress calculations are presented for a statically indeterminate union coupling.

The probabilities for nine electronic transitions among the low lying excited states in the C2 molecule are calculated by the dipole moment operator method and are given in the form of oscillator strength (or f values).

A technique for measuring extremely small temperature changes by means of a pyroelectric device is described. The sensing element is a short thin rod of polarized barium titanate ceramic with electrodes on the ends. The electric charges produced by changes in temperature are measured by a vibrating-reed electrometer. A number of calorimetric and noncalorimetric applications for the device are suggested.

The vibrational eigenvalues belonging to the ground electronic state of the HD<sup>+ and HT<sup>+ ions have been calculated. These calculations have been done for the J = 0 rotational state and neglecting the dynamic corrections to the potential. For the HD<sup>+ ion we find twenty-two bound states, and for the HT<sup>+ ion twenty three bound states.