The fjord-like inlets or sea-lochs which form so conspicuous a feature in the scenery of the west of Scotland stand in marked contrast to the shallow, low-shored firths of the east coast. When Dr John Murray decided to extend the physical and biological work of the Scottish Marine Station to the west coast he foresaw that many interesting conclusions were likely to be derived from the study of these isolated sea-basins. Various papers, published by him and other workers, contain preliminary discussions of many of the phenomena observed, fully justifying the anticipations which had been formed.For one year my work, as described in this paper, was carried out under the provisions of an Elective Fellowship in Experimental Physics of the University of Edinburgh, to which I had been elected in 1886; and subsequently by a personal grant from the Government Grant Committee for Scientific Research. The Committee also devoted several sums of money in payment of expenses in compiling this discussion. The Scottish Marine Station throughout gave the use of the steam-yacht “Medusa,” and the necessary apparatus.