﻿1861.] 



MURCHISOX AND GEIKIE HIGHLANDS. 



223 



We were now upon the ground rendered classic by the researches 

 of Hutton, Playfair, and "Webb Seymour, in which, with the memoir 

 of the last- mentioned of these eminent men in hand, we had only to 

 admire the truthfulness of their descriptions *, which show, even 

 down to the minutest details, the infinite ruptures of such strata, 

 their divergent directions, and their varied phases of metamorphism, 

 when in contact with or in the proximity of the syenites and green- 

 stones of the region. 



In fact, Playfair and his associate Lord Webb Seymour had here 

 collected specimens which in one and the same escarpment on the 

 left bank of the Tilt (not exceeding 600 feet in height) offered proofs 

 that granular limestone and quartz-rock were surmounted by mica- 

 slate and gneiss, the latter again alternating with thin quartzose 

 bands. The great variety of compound rocks detected by these close- 

 searching explorers, from a small area on the banks of the Tilt and 

 its affluents, at once demonstrated to us that along the flanks of the 

 Grampians there exists a richness and variety of mineral develop- 

 ment which is unknown in the oldest members of the series to the 

 north-west. Thus, Lord "Webb Seymour cites many compounds of 

 quartz, mica, felspar, hornblende, actinolite, compact dolomite t, talc, 

 steatite, and serpentine, mixed in a great variety of combinations 

 and in different proportions J. 



In the same tract of Glen Tilt we saw cause and effect admirably 

 displayed, as pointed out by Hutton, Playfair, and Seymour. "With 

 bosses of granite, syenite, and porphyry at hand (mere spurs, however, 

 of the gigantic granitic and porphyritic masses of the Grampians) we 

 at once understood how some of these younger crystalline strata 

 had been converted into the gneiss of the above-mentioned authors, 

 and had become associated here and there with granular quartz- 

 rock and limestone, in which the signs of their having been ori- 

 ginally sandstones and calcareous mudstones could not be doubted. 



The numerous disruptions in the tract east of Blair- Atholl have 

 thrown the strata into a multitude of fragments, as will be best 

 understood by referring to Lord "Webb Seymour's diagrams, and 

 particularly to plate 20 of his Memoir, in which upwards of forty 

 cases of the strike § and dip of the beds are given. "Whilst most 



* Not having with us the memoir of Lord Webb Seymour, we were indebted 

 to the Duchess of Atholl for the loan of it ; whilst the Duke laid open to us the 

 recesses of Glen Tilt by giving us as our guide his head-forester. 



t Lord Webb Seymour notes that compact dolomite is found in Glenelg and 

 Kintail. We also found there so much actinolite as to form, in fact, actinolite- 

 schist, with much talcose schist as well as granular limestone. It will therefore 

 be seen that the superior position we have assigned to the rocks of Kintail, 

 Loch-alsh, and Glenelg is borne out by their mineral characters also and their 

 similarity to the rocks of Glen Tilt. 



{ Trans. Roy. Soc. Edinburgh, vol. vii. p. 317. 



§ The word ' stretch ' has been used by these eminent Scottish geologists to 

 signify the direction as at right angles to the dip of the strata ; and we almost 

 regret that, unmindful of the earlier employment of this appropriate term, one 

 of us, in unison with Professor Sedgwick, was the first to recommend the 

 adoption of the word strike, from the German " Streichen " of German geolo- 

 gists. See Trans. Geol. Soc, 2nd series, vol. iii. p. 377 (note). 



