Dr. F. H. Hatch—The Wicklow Greenstones. 261 
amount of creeping in the second place will be nine times that in the 
first. And it seems hardly possible that there should in any country 
be nine separate frosts in one winter each penetrating to the depth of 
one foot. 
On the other hand, in arctic countries, the soil is permanently frozen 
at acertain depth, and the amount of creeping then depends on the 
depth to which the soil is thawed during a comparatively short 
summer. We may conclude, therefore, that the amount of creeping 
will be greatest in that place in which the soil frozen in winter, and 
also thawed in the following summer, attains its maximum depth. 
V.—Nores on THe WickLow GREENSTONES. 
: By Frepericx H. Haron, Px.D., F.G.8. 
(Communicated by permission of the Director-General of the Geological Survey.) 
HE Wicklow greenstones occur in sheets and dykes intrusive in 
the Lower Silurian slates (the equivalent of the Bala beds of 
Wales) that lie to the east of the main chain of the Leinster granite. 
Like the Welsh greenstones, they are associated with acid lavas 
(felsites and keratophyres) and felspathic tuffs, although of slightly 
later origin than these. 
In a petrographical appendix to the memoir on Sheets 188 and 
139 of the Map of the Irish Geological Survey, I have given 
some notes on the microscopical characters of the more important 
types. ‘These notes were based on sections made from rocks collected 
in June of last year. In November and December I had another 
Opportunity of visiting the ground, in company with my colleagues 
Messrs. Cruise and Clark ; and this visit threw fresh light on certain 
points not cleared up on the first occasion, especially with regard to 
the mechanically deformed greenstones, and also furnished me with 
an additional supply of material for microscopical investigation. As 
the publication of the memoir could not be delayed until this fresh 
material had been thoroughly worked out, perhaps I may be per- 
mitted to communicate in this place my results, coupled with a brief 
abstract of what has already appeared in the memoir. 
The Wicklow greenstones have this advantage over those of many 
other areas, that they present a greater variety in structure and com- 
position. Offering this attraction it is somewhat surprising that 
they have received such scant attention at the hands of the micro- 
scopist. The literature on the subject is indeed meagre, and may be 
disposed of in a very few lines.! Prof. von. Lasaulx,’ during a 
short visit to Ireland in 1876, collected some specimens which he 
described as diabase, diorite, and mica-diorite. ‘The Allport collec- 
tion in the British Museum contains a few sections of Wicklow 
greenstones. These have been described by Mr. Teall in his British 
Petrography.? 
1 Professor Haughton gaye a brief description, with two analyses, of the West- 
aston greenstone as early as 1859 (Trans. Roy. Irish Acad. vol. xxii. p. 619); 
but I am referring to microscopical work. 
2 «¢ Petrographische Skizzen aus Irland,” Tschermak’s Min. u. Pet. Mitth. vol. i. 
1878, p. 441. 3 1888, pp. 249 and 266. 
