[3] This remarkable section at the chalk quarries of Templepatrick the author has figured and described in the Physical Geology and Geography of Ireland, p. 99, 2nd edit. (1891), where the reader will find the subject discussed more fully than can be done here.
[4] These pebbles were first noticed by Mr. McHenry, of the Irish Geological Survey, in 1890.
[5] The vertical position of the columns of the Giant's Causeway is rather enigmatical. The Causeway cannot be a dyke, as has often been supposed, otherwise the columns would have been horizontal, i.e., at right angles to the sides of the dyke. Mr. R. G. Symes, of the Geological Survey, has suggested that the Causeway columns have been vertically lowered between two lines of fault, and that originally they formed a portion of the tier of beautiful columns seen in the cliff above, and known as "The Organ."
[6] Sleamish and several other of the Antrim vents are described by Sir A. Geikie in the monograph already referred to, loc. cit., p. 101, et seq. Also in the Expl. Memoirs of the Geological Survey of Ireland.
[7] A diagrammatised section of the Carrick-a-raide volcanic neck is given by Sir A. Geikie, loc. cit., p. 105.
[8] Geikie, loc. cit., p. 29, et seq.
[9] P. 32. The view that the crust of the earth has been horizontally extended by the intrusion of dykes is noticed by McCulloch in reference to the dykes of Skye.
[10] Hopkins, Cambridge Phil. Trans., vol. vi. p. 1 (1836).
[11] As suggested in my Presidential Address to Section C. of the British Association at Belfast, 1874.