open fissures. That it was poured out under water is again shown in the same interesting way just referred to, by the red sand which has been washed into the interspaces between the clinkers and has filled up the fissures, in which it is stratified horizontally between the walls. Above this band, and perhaps passing into it as its slaggy base, lies another more compact lava (_f_) like the lower sheets. [Illustration: Fig. 199.--General section across the Permian basin of Ayrshire. 1. Highest group of the Coal-measures; 2. Volcanic tuffs and ashy brick-red sandstones; 3. Lavas with interstratified tuffs and brick-red sandstones; 4. Brick-red Permian sandstones; 5, 5. Necks of volcanic agglomerate; 6. Boss of dolerite.] Throughout the series of lavas, as indicated in the foregoing section, traces of the pauses that elapsed between the separate outflows may be seen in the form either of layers of red sandstone or of tuff and volcanic breccia. Here and there, under the platform of bedded lavas, the brick-red sandstone is full of fragments of slag and fine volcanic dust. But the most abundant accumulation of such detritus is to be seen at the top of the volcanic series, where it contains the records of the closing phases of eruption. Thick beds of tuff and volcanic breccia occur there, interleaved with seams of red sandstone, like the chief mass of that rock, into which they gradually pass upward. Yet, even among the sandstones above the main body of tuff, occasional nests of volcanic lapilli, and even large bomb-like lumps of slag, point to intermittent explosions before the volcanoes became finally extinct and were buried under the thick mass of red Permian sandstone. [Illustration: Fig. 200.--Section of lavas east side of Mauchline Hill.] [Illustration: Fig. 201.--Section of the top of the volcanic series near Eastside Cottage, Carron Water, Nithsdale.]