ANNIVERSARY ADDRESS OF THE PRESIDENT. 1 37 



layers he noticed a number of the common shells and crinoids of 

 the Carboniferous Limestone sea. The formation of this neck took 

 place after the deposition of the Index Limestone, which is pierced 

 by it, and immediately to the west lies the Gair Limestone. It 

 would thus appear that the eruption which produced this funnel 

 gave forth only gaseous explosions, and took place on the sea-floor ; 

 further, that the low crater-walls were washed down to such an extent 

 that the sea entered and carried some of its characteristic organisms 

 into the lagoon within.^ 



(2) The majority of the rocks connected with the puys consist of 

 tuff or agglomerate. Externally they generally appear as smooth 

 rounded grassy hills that rise disconnected from other eminences. 

 In some districts their materials consist of a greenish granular tuff, 

 with rounded balls of various basic lavas and pieces of sandstone, 

 shale, limestone, or other strata through which they have been 

 drilled. This is their usual character in West Lothian. But in 

 other cases the tuff becomes a coarse agglomerate, made up partly of 

 large blocks of basalt and other volcanic rocks and partly of the 

 sedimentary strata around them, of which large masses, many cubic 

 yards in bulk, may be seen. 



Many examples might be cited where no lava of any kind has 

 risen in the vents, or where at least all the visible materials are of a 

 fragmentary character. But it is not infrequent to find small veins 

 and dykes of basalt which have been injected into the tuff or agglo- 

 merate. The finest illustration of this structure with which I am 

 acquainted is the Binn of Burntisland, in Fife, where the vent has 

 been so dissected by weathering that its walls strikingly remind 

 one of those of a crater. Narrow veins of black basalt may there 

 be seen threading their way as prominent ribs, standing out from 

 the crumbling slopes and crags of green tuif. 



(3) It has often happened that, after the explosions in a vent 

 have ceased, lava has risen in the chimney and finally sealed it up. 

 In such cases the main mass of the rock may consist of tuff or 

 agglomerate, with a plug of basalt, dolerite, or even more basic 

 material, of much smaller dimensions, in the centre or towards one 

 side. Binns Hill, West Lothian, and the Beith and Saline Hills of 

 rife are good examples of this structure. 



(4) In other cases no fragmental material is present in the vent, 

 or possibly one or two traces of it may be seen adhering to the walls 

 of the funnel, the prevailing rock being some form of lava. Necks of 



1 See Sheet 39, Geol. Surv. Scotland. 



