CHAP. XXXIII 
HISTORY OF INVESTIGATION 
113 
lorkshire at an early date attracted the attention of geologists. As far 
back as 1817, they had been the subject of a memoir by N. J. Winch, 1 who 
gave an accouirt of their effects on the adjacent rocks. More important 
were the subsequent papers on the same subject by Sedgwick, who, discussing 
the lithological characters, probable origin and geological age of the dykes, 
pointed out that while the Cleveland dyke was undoubtedly younger than a 
large part of the J urassic rocks, there was no direct evidence to determine 
whether dykes farther north were earlier or later than the time of the 
Magnesian Limestone. 2 Subsequent accounts of the dykes of the same 
region were given by Buddie, 3 M. Forster, 4 * 1ST. Wood, 6 * H. T. M. Witham, 6 
late ' and others, while in more recent years important additions to our 
knowledge of these dykes and of their effects have been made by Sir J. 
Lowthian Bell' 8 9 and Mr. .1. J. H. Teall. 0 
1 he geological age of the great series of Tertiary volcanic rocks has only 
been determined district by district, and at wide intervals. That some 
pait of the Antrim basalts is younger than the Chalk of that region was 
clearly shown by Berger, Conybeare and Buckland. Portlock, however, 
referred to the occurrence of detached blocks of basalt which he supposed 
to be immersed in the Chalk near Portrush, and which inclined him to 
believe that “ the basaltic flows commenced at a remote period of the 
Cretaceous system.” 10 Macculloeh showed that the corresponding basaltic 
plateaux of the Inner Hebrides were certainly younger than the Oolitic rocks 
of that region. But no nearer approximation to their date had yet been 
made when in the year 1850 the Duke of Argyll announced the discovery 
IJ t strata containing fossiliferous chalk-flints and dicotyledonous leaves, lying 
between the bedded basalts of Ardtun Head, in the Isle of Mull. 11 In the 
win e year these fossil leaves were described by Edward Forbes, who 
regarded them as decidedly Tertiary, and most probably Miocene. This was 
the first palaeontological evidence for the determination of the geological 
a ge of any portion of the basalt-plateaux, and it indicated that the basalts 
°f the south-west of Mull were of older Tertiary date. Taken also in con- 
nection with the occurrence of lignite-beds between the basalts of Antrim, 
it suggested that these volcanic plateaux were not due to submarine erup- 
2 Trails. Gcal. Soc. vol. iv. (1817), p. 21. See also Tilloch’s Phil. Mag. vols. xlix. and 1. 
s Cambridge Phil. Trans, vol. ii. (1827), pp. 21, 139. 
H rans. Nat. Hist. Soc. Northumberland, i. (1831), p. 9. 
°P. cil. i. p. 44 . 
' Op. at. i. J,,,. 305, 306, 308, 309. 
? °P- at. ii. (1838), p. 343 . 
Trans. Northumberland and Durham, ii. (1868), p. 30. 
9 Proc - Rr>V- Soc. xxiii. (1875), p. 543. 
'^Quart. Journ. Geol. Soc. xl. (1884), p. 209. 
of , Teporl on the Geology of Londonderry, p. 93. There can be 110 doubt that this was an error 
^0 serration. The Antrim basalts are all certainly younger than the Chalk. The supposed 
disco* 113 °* llaSalt " were l ,r °tably the ends of veins intruded into the Chalk, and perhaps partially 
roek° mieCtf,d the main P arts °f tllc veins - Su cli apparently detached masses of intrusive 
ot 1101 infrequent occurrence in connection with the Tertiary intrusive sills. An example 
mbe fottKi represented in Kg. 321. 
Frit. Assoc. Pex>ort, 1850, Sections, p. 70 ; and Quart. Jour. Geol. Soc. vii. (1851), p. 87. 
* uL. II j 
