Commission 14. (Wave-Lengths.)

Extract

Prof. Fowler expressed regret at the absence of Messrs Babcock, Burns, Kayser and Nagaoka.

In opening the discussion on sources of the primary standard, Prof. Fowler presented the following extracts from a communication which had been forwarded by Mr Babcock:

“The preliminary specifications adopted by the I.A.U. in 1925 are a simplified description of the Michelson lamp, naming the conditions which were at that time considered necessary and sufficient by Prof. Fabry himself. Even by implication they do not suggest a substitute for the original lamp. It goes without saying that a vacuum tube provided with internal electrodes is not intended for use with high frequency, but rather with the customary well-known type of excitation. In any case, before amending our specifications so as to prohibit high frequency excitation, at least three laboratories should agree that this is necessary.”