Transactions of the Royal Society of Edinburgh . 01 33 1-2 33 21-65 inches Such a section as this brings vividly before the mind a long-continuedintermittent feeble volcanic action during pauses between successive out-bursts of lava. In these intervals of quiescence the ordinary sediment ofthe lagoons accumulated and was mixed up with the debris, supplied by occa-sional showers of volcanic dust. Thin layers of sandstone, streaked withremains of the Carboniferous vegetation; beds of shale full of cypricl-cases,ganoid scales, and fragmentary ferns; thin beds of limestone, and bands of fire-clay
Transactions of the Royal Society of Edinburgh . 01 33 1-2 33 21-65 inches Such a section as this brings vividly before the mind a long-continuedintermittent feeble volcanic action during pauses between successive out-bursts of lava. In these intervals of quiescence the ordinary sediment ofthe lagoons accumulated and was mixed up with the debris, supplied by occa-sional showers of volcanic dust. Thin layers of sandstone, streaked withremains of the Carboniferous vegetation; beds of shale full of cypricl-cases,ganoid scales, and fragmentary ferns; thin beds of limestone, and bands of fire-clay supporting seams of coal, are interleaved with strata of tuff and sheets ofbasalt. Now and then a sharp discharge of larger stones would take place, asin the case of the block described by me some years ago as having fallen andcrushed down a still soft bed of coal.* These volcanic eruptions, however, did not seriously interfere with thelarger physical changes in progress over the whole region. Thus the depression Geol. Magazine, vol. i. p. CARBONIFEROUS VOLCANIC ROCKS OF THE FIRTH OF FORTH BASIN. 483 which led to the spread of a marine and limestone-making fauna over muchof central Scotland affected also this volcanic district. The limestones extendedover the submerged lavas and tuffs, which, however, in spite of the subsidence,continued for some time to be poured forth until the volcanic activity at lastceased, and the whole area went down beneath a deep mass of Carboniferousdeposits. Numerous illustrations might be taken from Linlithgowshire showing asimilar volcanic progress contemporary with ordinary quiet examples may suffice, one presenting intercalations of tuff, the otherassociated bands of lava. In fig. 22, we observe at the base a black shale (1)of the usual type. It is covered by a bed of nodular ?*m&*>» bluish grey tuff (2) containing black shale second black shale (3) is succeeded by a secondthin band of pale yellowish fine tu
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