The following observations of the temperature of the water at different depths below the ice covering Linlithgow Loch were made with one of Messrs Negretti & Zambra's “half-turn” self-registering thermometers, which proved to be a useful instrument for this species of inquiry. It was necessary, however, to fit it with a suitable inverting contrivance, as this part of the apparatus supplied by the makers is quite useless. The temperatures have received a provisional correction for error of graduation, and they may still have to receive a further, though certainly very slight, rectification, when a thorough comparison with a Kew standard has been made.