216 CoLte—On the Geology of Slieve Gallion, in the County of Londonderry. 
Map of Ireland* mark his growing appreciation of the complex character of the 
mass. 
O’Donovan,t in 1834, found the names Slieve (or Sliabh) Gallan, Callann, and 
Gallion, all in use, and states that the range was probably named from the giant 
Callann Mor. This hero is said, by-the-by, to be buried in Carnanbane, on the 
moorland-slope above Lough Fea. 
Whitley Stokes,t in 1838, has an odd little reference to ‘ globules of quartz” 
occurring in the “‘ limestone of Slieve Gallion” ; and his comparison of these with 
the pebbles of the mulatto-stone of other areas is aptly confirmed by the work of 
Mr. Egan,§ who found what is practically the ‘‘ Hibernian Greensand” i situ 
on Slieve Gallion North. 
Portlock’s ‘‘ Report on the Geology of the County of Londonderry and of parts 
of Tyrone and Fermanagh,” appeared in 1843, and contains a number of new 
observations on Slieve Gallion. The theoretical deductions must now-a-days, 
however, be received with considerable caution. 
Prof. J. B. Jukes’s geological map of Ireland (1870) shows all the rocks of 
Slieve Gallion as either granite or of metamorphic origin; but Prof. Hull was 
enabled, in his revision of the map in 1879, to insert a larger amount of detail. 
Mr. Nolan’s results were published in the same year,|| and include, as we shall see, 
some very remarkable advances towards an understanding of the district. The 
Geological Survey of Ireland issued sheet 27, including the main mass of Sheve 
Gallion, in 1880, and sheet 26, containing the wild moorlands to the west, m 1882. 
The corresponding memoirs, by Messrs. I’. W. Egan and Joseph Nolan respectively, 
are dated 1881 and 1884. 
In 1889, the Longitudinal Section, sheet 27, including a traverse of Slieve 
Gallion, completed the work of the Survey. E. T. Hardman ] had already, in 
1876, published a section across the mountain, which differs so far from that of 
Portlock as to suggest independent observation. Both this and the map 
accompanying it may, however, be set aside, now that we have the more detailed 
results provided by Mr. Egan. 
The valuable ‘‘Guide” of Messrs. McHenry and Watts** naturally contains 
* Portlock, ‘‘ Report on Geol. of Londonderry,” pp. 77 and 81. I have been unable to trace the edition 
- of 1838 referred to by Portlock, and many copies of the map of 1839 contain the changes attributed by 
Portlock to that of 1842. These may, however, have been subsequently coloured on sheets printed off in 1839. 
{ Op. cit., MS., p. 225. 
+ “On Globular Formations,” Journ. Geol. Soc. Dublin, vol. i., p. 18. 
§ Mem. sheet 27, p. 29. 
|| ‘On the Metamorphic and Intrusive Rocks of Tyrone.” Geol. Mag., 1879, p. 154. 
{ ‘On the Age and mode of Formation of Lough Neagh, Ireland.” Journ. R. Geol. Soc. Lreland, vol. 
iy., plates xi. and xii. 
** “© Guide to the Collections of Rocks and Fossils, Geol. Surv. of Ireland” (1895), p. 73. 
