In this issue

USEFULNESS of the cathode ray oscillograph has been extended greatly by development of means for using it as a multielement instrument. Two types of equipment for this purpose are described in 2 papers in this issue: One describes an electron tube circuit which enables 2 or more waves having frequencies in simple multiple relationship to each other to be portrayed (pages 1095–1100); the other describes mechanical auxiliaries for use in circuits that permit of the repeated application of the waves to be observed (pages 1045–7).