1885.] Age of the Tertiary Basalts of the Atlantic. 413 



through each bed in tarn, and dipping beneath the sea at the other 

 extremity. On the coast, near the centre of the head, occurs a small 

 chine, apparently due to the weathering out of a vertical dyke, which 

 has cut through the gravels and shales, and left them in a very 

 accessible position ; it was here, accordingly, that T resolved to excavate 

 them. 



With the assistance of the Duke of Argyll's energetic factor, Mr. 

 Sinclair, men and tools and a barrel of powder were forthcoming, 

 and after a few days' work and the removal of a mass of the intensely 

 indurated shingle bed, to the extent of perhaps hundreds of tons, many 

 square yards of the whinstone and the underlying black shales were 

 exposed. The large specimens of Platanites aceroides and Onoclea 

 hebridica, now exhibited, were the results. The new specimens of the 

 latter, including fertile as well as barren fronds, give a very different 

 idea of its growth to what would have been imagined from those 

 formerly known, and we see that the pinnae were produced on very 

 long and stout naked stems. The ravine, however, proved an unfor- 

 tunate selection, for the whinstone became poorer in fossils as we got 

 farther in, and the underlying black shales, though crowded with 

 leaves, proved so squeezed and full of slickensides or faulted surfaces, 

 and, consequently, so brittle as to be practically valueless for collect- 

 ing purposes. The lighter limestone is wholly absent at this spot. 

 From the condition of the shales and calcined appearance of the 

 gravels — here of a steely-grey colour, intensely hard, with pure white 

 and occasionally cherry-coloured flints, it is evident that the ravine 

 must be the site of an old dyke, and if proof were wanting of a violent 

 upthrust at this spot, it is to be found in the upturned edges of the 

 bottom bed on the west face. The succession of beds in the section 

 we had been so laboriously working at in the ravine, in no way pre- 

 pared me for the discovery I made subsequently, that within 100 yards 

 there existed, many feet below the lowest sedimentary bed present in 

 the ravine, a deposit of limestone, rivalling in fineness and texture 

 the celebrated lithographic stone of Solenhofen, and containing, as 

 expressed by Professor Newberry, "most exquisitely preserved leaves.' ' 

 On removing some turf, in order to obtain a true section, I was over- 

 joyed to find this deposit, so completely different in character to any 

 previously seen in the basalts. It may seem strange that it should 

 have been overlooked by the many geologists who have visited the 

 spot ; but the beds are in a very inaccessible position, and to work 

 them dangerous, until sufficient had been worked away to afford 

 standing room. Quarrymen could not be induced to work there at 

 all, but two boatmen did not make any objection. 



It is too early to attempt as yet to give any account of the new 

 flora, which seems to differ considerably from that of the shales above. 

 Very large leaves of many kinds occur in the clay at the base, which 



