284 [Proc. B.N.F.C, 



The tickets being available for fourteen days, many took the 

 opportunity of seeing a little more of the country, so full of 

 interest to naturalists and antiquarians. 



29 Julv* 

 THE MOURNES. 



The sixth excursion was held on the 29 July to the Mourne 

 mountains, in conjunction with the London Geologists' Asso- 

 ciation, who were then visiting the North of Ireland. A party 

 of about eighty arrived at Newcastle at 9-30, where breakfast 

 was partaken of at Lawrence's rooms at the station. Breakfast 

 finished, the brakes and cars were mounted, and the road taken 

 to the Trassey Bridge. Here the machines were left, and the 

 party proceeded up the valley to the Hare's Gap, close to which 

 are the Diamond Rocks ; these are great masses of Mourne 

 granite, containing very numerous drusy cavities, some of them 

 of considerable size. So often have they been visited by geologists 

 that parts of the hillside bear quite a resemblance to a quarry. 

 These cavities contain large and well-formed crystals of smoky 

 quartz, orlhoclase, biotite, albite, and less frequently of beryl, 

 topaz, and microcline. Of all these many capital specimens were 

 taken by the members, the topaz and beryl crystals being 

 very good. From this point the party broke up into four 

 divisions, one contingent walking back to the cars, 

 another going round the flank of Commedagh to " the 

 castles," which consist of the usual granite, whose 

 subcolumnar structure in this part gives rise to vertical 

 and horizontal jointing produced by shrinkage during the 

 cooling of the mass. This jointing has been so increased and 

 brought out by the action of wind and rain, snow, frost, and sun 

 that the masses now present the appearance of huge bastions 

 and fortifications of Cyclopean masonry. A third section of the 

 party walked up over Slieve Commedagh (2,512 feet), and a 

 venturesome few even ascended Donard afterwards and observed 



