COMMUNICATION 
TO THE 
MONTHLY MEETINGS 
OF THE 
YORKSHIRE PHILOSOPHICAL SOCIETY, 
1874 . 
October 6th. — Dr. Procter read a paper on Basalt in 
the North of Ireland, and its formation,” of which the follow¬ 
ing is an abstract:— 
He first described its distribution over that country, espe¬ 
cially as it constitutes the Giant’s Causeway. Basalt is 
part of a series which, when w^ell marked, was composed of (1) 
basalt, (2) pisolitic iron ore, which is now extensively worked 
in Antrim, (3) hole, which gradually passes into (4) litho- 
marge. After describing the characters of the prismatic form, 
he considered the beds of lignite which alternate with the 
basalt. The volcanic origin of basalt is shown by its general 
character, the gradations which are observed from pumice to it, 
as well as its occasional deposit, being as it were in sheets, 
coupled with the metamorphic action due to heat manifested in 
its proximity. In rocks of all ages fissures occur from various 
causes; if into these fissures a quantity of molten basalt is 
injected, then a basalt dyke is formed, or the liquid matter may 
overflow the dyke and spread far over the surrounding country, 
and this is precisely the state of things in Antrim. The true 
nature of the change is indicated by the condition of the 
surrounding formations. In that locality it is the chalk which 
is traversed by the basaltic dykes. Near the basalt the chalk 
is converted into granular marble, which is greatest at the point 
of contact; from thence it gradually decreases until its normal 
