At times my walks were directed along the sea-shore. Naturalists well know how much the western coasts of Scotland differ in their productions from its eastern ones; but it was a difference wholly new to me at this time; and though my limited knowledge enabled me to detect it in but comparatively few particulars, I found it no uninteresting task to trace it for myself in even these few. I was first attracted by one of the larger sea-weeds, _Himanthalia lorea_--with its cup-shaped disc and long thong-like receptacles--which I found very abundant on the rocks here, but which I had never seen in the upper reaches of the Moray Firth, and which is by no means very common on any portion of the east coast. From the sea-weeds I passed to the shells, among which I detected not only a difference in the proportions in which the various species occurred, but also species that were new to me--such as a shell, not rare in Gairloch, _Nassa reticulata_, but rarely if ever seen in the Moray or Cromarty Firths; and three other shells which I saw here for the first time, _Trochus umbilicatus_, _Trochus magus_, and _Pecten niveus_.[5] I found, too, that the common edible oyster, _ostrea edulis_, which on the east coast lies always in comparatively deep water, is sometimes found in the Gairloch, as, for instance, in the little bay opposite Flowerdale, in beds laid bare by the ebb of stream-tides. It is always interesting to come unexpectedly either upon a new species or a striking peculiarity in an old one; and I deemed it a curious and suggestive fact that there should be British shells still restricted to our western shores, and that have not yet made their way into the German Ocean, along the coasts of either extremity of the island. Are we to infer that they are shells of more recent origin than the widely-diffused ones? or are they merely feebler in their reproductive powers? and is the German Ocean, as some of our geologists hold, a comparatively modern sea, into which only the hardier mollusca of rapid increase have yet made their way? Further, I found that the true fishes differ considerably in the group on the opposite sides of the island. The haddock and whiting are greatly more common on the east coast: the hake and horse mackerel very much more abundant on the west. Even where the species are the same on both sides, the varieties are different. The herring of the west coast is a short, thick, richly-flavoured fish, greatly superior to the large lean variety so abundant on the east; whereas the west-coast cod are large-headed, thin-bodied, pale-coloured fishes, inferior, even in their best season, to the darker-coloured, small-headed variety of the east. In no respect do the two coasts differ more, or at least to the north of the Grampians, than in the transparency of the water. The bottom is rarely seen on the east coast at a depth of more than twenty feet, and not often at more than twelve; whereas on the west I have seen it very