Geikle — Permian Volcanos in Scotland, 



247 



of their colour, ranging from a brick red to bright orange, by their 

 abundant false-bedding, their thick beds, their entire freedom from 

 shale of any kind, and their clear granular quartzose texture. Now, 

 beds of sandstone having this character, and identical in every 

 respect with the recognised Permian sandstones of the basin, lie 

 among the fine ash and peperino below the sheets of trap, similar beds 

 are intercalated between the beds of trap, they occur again in the 

 ashy deposits overlyiag the trap, and there they can be seen to form 

 part of the ordinary sandstones of the Permian basin. This latter 

 junction is singularly instructive. It is well seen along the banks of 

 the river Ayr at Ballochmyle where bed after bed can be studied from 

 the massive brick-red sandstones down into the tuif that overlies the 

 melaphyres. The subjoined woodcut (Fig. 2) illustrates this section. 

 At the bottom lies the dull-red stratified tuff — a truly volcanic rock 

 -consisting of nothing but angular, subangular, and rounded fragments 

 of different felspathic traps, imbedded in a triturated paste of the 



vV«^^f!i4':teWi«|;i|^^^^i'^^^ 



Fig. 2. — Section of Pek,mia.n Sandstone anb Tiftp. River Aye, Ballochmyle. 



same materials. Some of the stones are slaggy lumps of rock, like 

 "volcanic bombs, and in one case I found the air-cells pulled round 

 the spheroidal surface of the mass — ^the riesult perhaps of the whirl- 

 ing of the bit of melted lava through the air at the time of ejection. 

 In the upper part of the tuff, thin lenticular seams of brick-red sand- 

 stone, sometimes mingled with ashy material, make their appearance, 

 and these increase in number until they shade up into the main mass 

 of the Permian sandstones. The gradual cessation of the tuff is full 

 of interest, for we find that even after havLag passed over the highest 

 of its beds we still meet with occasional nests of volcanic lap>iRi and 

 smgle stones in the red sandstones. In this section we see how the 

 igneous forces with intermittent and continually decreasing showers 

 of ash and stones, finally died out. 



It thus appears that the volcanio rocks of this part of Ayrshire lie 

 upon, are interstratified with, and are covered by red sandstones, 

 which have a distinctive character throughout as parts of one series 

 marked off from the Carboniferous sandstones on which they rest. It 

 is admitted that these red sandstones are Permian ; it follows that 



