9 2 



[Proo. B.N.F.C, 



liquid being readily obtained with the Westphal balance. From 

 a consideration of the densities of a number of minerals it was 

 shown that the specific gravity of a mineral depends largely on the 

 chemical nature of the substances of which it is composed, and 

 also to some extent on the state of molecular aggregation. The 

 densities of igneous rocks also bear out these two general con- 

 clusions, as the specific gravity increases with the amount of 

 crystallisation that has taken place, and increases as the percentage 

 of silica decreases. Heavy solutions are used to separate the 

 mineral constituents of sands and rocks, the minerals being 

 deposited in order of density as the liquid is diluted. During the 

 course of the lecture Mr. Dewhurst exhibited many pieces of 

 apparatus, and demonstrated the methods of obtaining specific 

 gravity in the case of each instrument. 



"church island." 



A meeting of the Archaeological Section was held on the 

 evening of the 3rd February, in the Museum, College Square 

 North— Mr. W. J. Fennell, F.R.I. B.A., presiding — when Mr. 

 Joseph Skillen read a paper on " Church Island," illustrated with 

 lantern views. He first described an ancient stone monument in 

 the neighbourhood of Ballyrnena, consisting of a stone circle and 

 kist-vaen, unmarked on the ordnance survey map. Church Island, 

 the lecturer pointed out, was situated in Lough Beg, close to the 

 shores of County Derry. On it stands an old church of great 

 antiquity, graced by a modern spire erected by the Bishop of 

 Derry, Earl of Bristol, in 1778. Many of the eccentricities of this 

 nobleman-prelate were referred to, as was also his association with 

 the Ulster volunteer movement. The most interesting remains, 

 apart from the church, is a holy well which the lecturer described 

 — the well consisting of a hollowed stone, resorted to yet by the 

 peasantry for cures, as the rags which adorn the ancient thorns 

 attest. During the wars in 1642 the church was held as a military 



