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In some districts hornfelsed rocks occur which have acquired a schistose structure through shearing, and these form transitions to schists and gneisses which contain the same minerals as the hornfelses, but have a schistose instead of a hornfels structure.

Among these may be mentioned cordierite and sillimanite gneisses, andalusite and kyanite mica schists, and those schistose calc silicate rocks which are known as cipolins.

In these biotite hornfelses the minerals, which consist of aluminium silicates, are commonly found; they are usually andalusite and 711 sillimanite, but kyanite appears also in hornfelses, especially in those which have a schistose character.

This tendency to decaying in the heart may be attributed to the coldness of the schistose sub-soil upon which the trees are rooted, as well as to the perpetual moisture of the climate above alluded to.

Here we first noticed the character of the vegetation in the Strait, as so different from that of Cape Gregory and other parts of the Patagonian coast, which is mainly attributable to the change of soil; the northern part being a very poor clay, whilst here a schistose sub-soil is covered by a mixture of alluvium, deposited by mountain streams; and decomposed vegetable matter, which, from the thickness of the forests, is in great quantity.