108 Obituary Notices of Felloivs deceased. 



a group of porcellanites, volcanic breccias, and felstones for which he 

 proposed the name Pebidian ; the lower, consisting of highly crystal- 

 line rocks, which, however, he supposed had formerly been sediments, 

 and called Dimetian. Next year he showed that similar rocks 

 occurred in other parts of Pembrokeshire ; in the following one, he 

 separated under the name Arvonian, a group of halleflintas, breccias, 

 and quartz-felsites, which at first, so far as recognised, had been taken 

 for the lower part of the Pebidian ; recurring to that subject in later 

 papers. 



(3) Closely allied to this group of papers is a third one, begun in 

 1878 dealing with the Pre-Cambrian rocks of Carnarvonshire and 

 Anglesey. In this district also Hicks maintained that an important 

 series existed which was capable of sub-division into Dimetian, 

 Arvonian and Pebidian. Here we may mention his interesting dis- 

 covery, announced in 1868, of plant remains at the base of the Denbigh- 

 shire Grits near Cor wen. Over the Pre-Cambrians of Pembrokeshire 

 and North Wales many battles have been fought and peace has not 

 yet been proclaimed. Not a few geologists think Hicks to have been 

 right in asserting the existence of a Pre-Cambrian series, containing 

 both comparatively unaltered, and highly crystalline rocks, but that 

 he was premature in attempting a definite classification. His Arvonian 

 embraced rocks of very different characters, the most recognisable 

 types of which seem better left with the Pebidian, while the original 

 Dimetian (though a crystalline series undoubtedly exists), rested on an 

 insecure foundation. 



(4) In 1883 he boldly attacked the problem of the Scotch Highlands in 

 a paper on " The Metamorphic and Overlying Rocks in the Neighbour- 

 hood of Loch Maree." In this he asserted that though the Glen 

 Laggan section exhibited, as Murchison had maintained, an upward 

 succession from the Torridon Sandstone to the so-called Newer Gneiss, 

 the lattejr was not a highly altered rock, but that far behind it (in 

 Glen Docherty) members of the Lower Gneiss series again rose up, and 

 then passed southwards into the massif of the Central Highlands. The 

 question was far too intricate to be settled in a comparatively short time, 

 and his attack on the Murchisonian position was generally held to have 

 failed ; at the same time he had shown, and this was made yet clearer 

 in two subsequently published papers on the Central Highlands, that the 

 crystalline schists and gneisses, formerly mapped as Newer Gneiss, and 

 regarded as metamorphosed Silurian, cannot be separated from the 

 crystalline rocks beneath the Torridon Sandstone in the north-west. 

 This is now generally admitted; the key to the enigma being the 

 discovery of Professor Lapworth. 



(5) This group deals with the other extreme of geological history. 

 Boulder clays and some gravels occur near Hendon, and fragments 

 of Mammalian bones have been exhumed in the vallev below his 



