736 D. MACKINTOSH ON SOME NEW SECTIONS 



What could have obliterated all signs of the interval during which 

 the change from non-glacial to glacial conditions took place? The 

 revolution in temperature may certainly have occurred during an 

 intervening period when dry land existed. But as there are no 

 traces of a land-surface, so far as I have seen, between the middle 

 sand and upper-clay, I would suggest that the commencement of 

 the upper-clay submergence may have been sudden, so as to gene- 

 rate an earthquake-wave capable of accomplishing the sweeping 

 denudation of the sand which is so forcibly suggested by the clean 

 and persistent line of separation above described. 



Striated Rock-surfaces and their Relation to the Direction in which 

 Erratic Stones have been carried. — I very lately saw a fresh exposure 

 of intensely striated rock, from which a covering of upper Boulder- 

 clay had been removed. It is a part of a more extensive display 

 which has been demolished by quarrying operations, and occurs 

 about a quarter of a mile south of St. James's Church, Birkenhead. 

 The stria?, including large grooves, point to between 2b° and 30° 

 west of N. A short distance southward I found striae pointing W. 

 30° S. As the extent to which the directions of the striae vary in 

 the neighbourhood of the estuaries of the Dee aud Mersey does not 

 seem to be generally known, I would state that I have seen an 

 extensive series near St. Silas's Church (north of Prince's Park, 

 Liverpool) pointing 1ST. 35° W., with a few cross striae running 

 between K 38° W. and N. 40° W. In Toxteth Park, Liverpool, 

 Mr. Morton, F.G.S., has found striae pointing N. 42° W. ; at Kirk- 

 dale, N. 15° W. ; and at Oxton, Birkenhead, N. £0° W. I have re- 

 examined grooves (including one more than three inches in breadth) 

 close to the new Mission-house, Borough B,oad, Birkenhead, which 

 were first noticed by Mr. Bostock, and found them pointing N. 45° 

 W. If we connect these instances with that found on the east side 

 of Hope Mountain, near Caergwrle, where I found the striae pointing 

 to about N". 45° W., we shall have striae ranging from N. 15° W. to 

 K. 45° W., which will include the main directions in which erratic 

 stones (including Cumberland and Kirkcudbrightshire granite and 

 Irish chalk-flints)* have travelled from their respective points of 

 dispersion, though we have no reason to suppose that they travelled 

 in straight lines. As Mr. De Ranee lately observed at a meeting 

 of the Liverpool Geological Society, these striae can be much better 

 explained by floating ice than by land-ice ; and it may be added 

 that the floating ice may have been blown by wind as well as car- 

 ried by currents, as proved by observations made by the late Austro- 

 Hungarian Expedition in the neighbourhood of Franz Josef Land. 

 It is well known that the directions of the striae above noticed are 

 crossed in the Isle of Man by striae from the E.N.E., and in Anglesey 

 by striae from between N. 25° E. and 30° E., — that is, from the direc- 

 tion of the Lake-district. In Anglesey there are true roches mou- 

 tonnees (Geol. Mag. for Jan. 1872), but there are no decided instances 



* These flints are most numerous about Parkgate. They thin out S. and S.E. 

 until they come into collision with flints from the eastern counties, which thin 

 out westward. 



