28 



MR. LYELL ON THE PROOFS OF A GRADUAL RISING OF 



of the water ; and its extreme length from east to west, including a detached point at 

 one end, measured fifty-two feet four inches and a half. 



From Gulholmen I went to Marstrand, an island about twenty miles to the south, 

 in order to observe another of the marks enumerated by Bruncrona. I first re 

 crossed the ferry at Svansund to the main land, and then passed to that of Tjufkil, 

 which leads to Koon. On the shore at Tjufkil I found a bed of oysters and other 

 shells, five or six feet thick, with pebbles intermixed, rising to the height of sixteen 

 feet or more above the water. The oysters, which were ingreat number, all belonged 

 to the Ostrea edulis, which is taken on this coast ; and the other shells were the same 

 as at Uddevalla and EUelos, with the addition oi Anomia striata. This shelly deposit 

 has been ovei-whelmed by a great fall of rock from the steep heights of gneiss behind, 

 some of the fragments which cover the shells being about nine feet square. 



Not far from the harbour at Marstrand is an artificial channel, which, in the year 

 1770, was cut through an isthmus which formerly connected two parts of Koon 

 island. The excavation was made through a mass of clay and sand with shells, simi- 

 lar to that of Tjufkil, already mentioned ; so that there can be no doubt that there 

 must originally have been a natural passage in this place. One Captain Constant, 

 who superintended the digging of the channel in 1770, caused a mark, of which the 

 following is a sketch, to be hewn on the face of a vertical rock of micaceous schist 

 on the shore of Koon, nearly opposite Marstrand. 



Fig. 14. 

 Mark at Koon Island, near Marstrand. 



An horizontal line, ten inches long, is seen twenty-one inches below the bottom 

 of the last cipher. This line I found to be just ten inches above the level of the 



