In the dikes the mineralogical composition is tolerably constant, and specimens selected from different points show no notable difference except that they are usually less decomposed than the coarse grained varieties. Within the larger bodies, where cooling may be considered to have been slower, a series of rock types differing from one another in mineral composition, and consequently in physical appearance, are associated. At many localities these differentiated varieties are intimately intermingled, so that within an area of a few square yards almost the whole series may be found. Conditions of this sort were first and best observed in the Lett properties on Wapus creek, where the extensive stripping and trenching greatly facilitated geological study. A suite of specimens was obtained which exhibit an unbroken gradation from ordinary gabbro to the fine grained pink rock known as aplite. With a decreasing pyroxene content and increasing abundance of feldspar the rock grades from a dark green diabase at the basic end through a reddish phase into a type which, in the field, might be termed a syenite, being of granitic texture, red colour, and without visible quartz. These phases are cut by aplite dikes which at first glance do not very closely resemble them, but their comparison has shown that they too include a group whose coarsest and most basic form does not differ greatly from the syenitic type of the diabase series. From a pale flesh-coloured rock of fine granitic texture in which a little dark mineral is visible, the successive phases of the aplite graduate toward a dike material of light pink colour and saccharine texture almost devoid of ferromagnesian constituents. _Microscopic character._—The consanguinity of diabase and aplite is further established by microscopic study. It was intended to make a somewhat complete comparative study; but, at the outset, the materials, although fresh looking in the hand specimens, were found to be much decomposed, sometimes so completely that the original composition could not be satisfactorily inferred, and an outline must suffice therefore until fresher material is secured.