W. A. E. Ussher — Historical Geology of Cornwall. 29 



Fourthly, the insulation of St. Michael's Mount and the identifi- 

 cation of Ictis. 



Part 1. — Contemporary Observations. 



These have been taken exclusively from papers by Mr. Edmonds. 

 In Edin. New Phil. Journ. he mentions an influx and reflux of the 

 sea, varying from three to above five feet, in Mounts Bay, at five p.m., 

 on March 23rd, 1847 ; the double movement taking from fifteen to 

 twenty minutes. During the most part of the day the water, from 

 the mouth of the Catwater to within Sutton Pool, at Plymouth, 

 was constantly agitated by flux and reflux. 



In Falmouth Harbour, and on the shores of the Scilly Isles, 

 similar oscillations took place, whilst in St. Ives Bay nothing un- 

 usual was remarked. 



At Newlyn four fluxes and refluxes of the sea occurred in an hour 

 and a half. In the shallow water between Marazion and Penzance 

 no agitation was perceptible. The limits of the disturbance, so far 

 as observed, were from Mousehole on the west to Porthleven on the 

 east, a distance of ten miles. 



On October 30th of the same year, at five p.m., a rise of the sea, 

 coming from the south-west, and reaching five feet, took place at 

 Penzance. 



Three similar fluxes and refluxes occurred at Plymouth in forty 

 minutes. 



Four whirlwinds, accompanied by shocks, passed through the 

 parish of St. Just, on December 12th, 1846. 



The same writer 1 mentions an earthquake felt over 100 miles, 

 from the Scilly Isles through Cornwall as far as Plymouth, in 

 July, 1757. 



A disturbance of the sea took place in Mounts Bay at four hours 

 and a quarter after the great earthquake at Lisbon in 1755, when 

 the sea suddenly rose to the height of six feet at St. Michael's 

 Mount, coming in from the S.E. ; and to eight feet at Penzance 

 Pier, coming in from the S.E. and S.S.E. At Newlyn Pier -and 

 Mousehole the sea coming in from the south rose and fell ten feet. 

 Toward the decline of the commotion, the sea was found to be 

 running at seven miles an hour in Guavas Lake. 



If the observation recorded in the following extract be not mag- 

 nified in transmission from the original observer, it shows the care 

 necessary in ascribing the occurrence of some isolated pebbles and 

 boulders above the reach of the highest spring tides to changes 

 in the relation of sea and land : " I have been informed by two 

 descendants of an eye-witness that at Lamorna Cove, which is on 

 the south-east part of Mounts Bay, the sea on this occasion rushed 

 suddenly towards the shore in vast waves with such impetuosity 

 that large rounded blocks of granite from below low-water mark 

 were swept along like pebbles, and many were deposited far above 

 high-water mark. One of seven or eight tons weight was rolled 

 to and fro several feet above high-tide level." 

 1 T. E. G. S. Corn. 



