In January I read a paper on the salinity of the Firth of Forth, in which the law governing the distribution of salt in that estuary was pointed out. It appeared that in the eastern or seaward part of the Firth the change in mean salinity per mile was very slight, and the tidal range was small, while both decreased gradually as the sea was approached. On the other hand, the riverward half of the Firth showed a rapid alteration in density along its length, and a correspondingly great range between high and low tide.