this line there is often a strongly marked division into layers of different salinity and temperature, especially in summer and autumn, when the fresher water of the Irish Channel is found overlying the salt water of the Bay of Biscay. The salinity of the English Channel undergoes an annual change, being highest in winter and spring and lowest in summer, and this change is better marked in the eastern area, where the mean deviation from the annual mean reaches 0.3 pro mille, than it is farther west with a mean deviation of 0.1 pro mille. There is also reason to believe that there is a regular change with a two-year period, years of high maximum and low minimum alternating with years of low maximum and high minimum. Variations of long period or unperiodic also occur, which are probably, and in one case (1905) almost certainly, due to changes taking place some months earlier far out in the Atlantic Ocean. The mean annual _surface_ temperature increases from between 11° C. and 11.5° C. at the Strait of Dover to over 12° C. at the western entrance.[1] The yearly range in the eastern area is considerable, reaching 11° C. off the Isle of Wight and 10° C. in the Strait of Dover; westward it gradually decreases to 5° C. a short distance north-west of Ushant. The mean maximum temperature, over 16° C., is found under the English coast from Start Point to the Strait of Dover about the 1st of September and off the French coast eastward of Cape la Hague about eleven days later. In the western area the maximum temperature is about 15° C. and occurs between September 1 and 11. The mean minimum surface temperature is between 5° C. and 6° C. at the eastern end, and increases to over 9° C. off the coast of Brittany. Owing to the thorough mixing of the water in the eastern area the temperatures are here generally the same at all depths, and the description of the surface conditions applies equally to the bottom. In the western entrance, on the other hand, the bottom temperature is often much lower than on the surface; the range here is also much less, about 3° C., and the maximum is not reached till about the 1st of October, or from three weeks to a month later than on the surface. A detailed account of the mean conditions in the English Channel will be found in _Rap. et procès-verbaux_, vol. vi., and _Bulletin supplémentaire_ (1908) of the Conseil Permanent International pour l'Exploration de la Mer (Copenhagen). (D. J. M.)