Cole — The VanoUte of Annalong, Co. Down. 519 



basic dykes which are probably contemporaneous with the plateau- 

 basalts of Co, Antrim ? 



In addition to the friends already named, I have to thank 

 Mr. W. W. Watts, M.A., for kind help given with regard to tlie 

 Survey specimen. Much of the detailed work has been carried on 

 in the Geological Laboratory of the Eoyal College of Science for 

 Ireland. The credit for the discovery and just appreciation of the 

 variolite of Mourne rests with the officers of the Geological Branch 

 of the Survey of Ireland some fifty years ago. 



EXPLANATION OF PLATE XXL 



Fig. 1. — -Edge of the variolitic dyke of Annalong, in contact with the 

 sedimentary rocks. Banded and fluidal structures in brown 

 tachylyte, with porphyritic felspar and elongated vesicles. 

 X 11. 



Fig. 2. — Variolite of Annalong, showing ordinary spherulites, and 

 spherulitic matter aggregated round a porphyritic group 

 of pyroxene and plagioclase felspar, x 11. 



Fig. 3. — Variolite from the S.E. end of the dyke of Annalong, showing 

 abundant and often curving skeleton-crystals, x 1 1 . 



Fig. 4. — Part of the same section enlarged, showing dark mierolites (mag- 

 netite), which under a lower power are seen to form parts of 

 skeleton-crystals ; colourless ones (probably felspar) ; and 

 pale green longer rods (pyroxene ?). The last-named often 

 show " palisade -structure." A curving row of pyroxene 

 granules, in contact with one another, is also seen, x 200. 



