University and Educational Notes

THE investigation of the spectrum of helium in the extreme ultra-violet, on which I have been long engaged, and which had pretty nearly come to a standstill for want of an untarnished diffraction grating, has recently been set in motion again by the energy and kindness of Prof. R. W. Wood, who has furnished me with several instruments from the engine at Johns Hopkins University. As a result I am able to make some additions to the facts already announced.