I MUST confess that I was surprised by Mr. R. E. Baynes' communication, in NATURE, vol. xix. p. 33, that the galvanometer I have proposed in NATURE, vol. xviii. p. 707, has already been described.

SINCE it was thought that interesting experiments might be performed if it were possible to measure quantitatively persistent currents in a supraconducting circuit much smaller than have so far been ...