BRAVAIS ON LINES OP FORMER SEA-LEVEL IN FINMARK. 549 



taken place in recent geological periods, affecting the relative level 

 of land and sea, are not confined to the Scandinavian peninsula, 

 and possibly there are few lines of coast that will not offer them on 

 close investigation. They have been recorded on the shores of 

 Spitzbergen, in the north of Scotland, in several places on the 

 coast of England, and the coasts of France do not seem to form an 

 exception to the general law. But in approaching the temperate 

 zone indications of this change are found to be frequently obli- 

 terated by various agricultural and other operations, so that it is 

 hardly possible to compare the phenomena in these districts. 



The establishing the possibility of tracing these lines of ancient 

 level for a considerable distance, and the placing beyond a doubt 

 the continuity of the line observable only at detached points ; the 

 existence in Finmark of two distinct lines of this kind, and of 

 one less certain ; and lastly the proof that the lines are neither 

 strictly parallel to one another or to the present level of the Arctic 

 Sea : — these may be considered the general results of the labour 

 here recorded. 



With regard to the numerical data, they are not at present so 

 important as might be wished, owing principally to their isolation 

 and the smallness of their number ; but they will increase in im- 

 portance in proportion as additional exact observations furnish 

 new documents to this pre-historical hydrography. Thanks to 

 the enlightened care of the Norwegian government, even the least 

 accessible districts of that country are becoming more accessible, 

 especially to those sons of the north, so zealous and so learned, to 

 whom we are indebted for the great and rapid advances that have 

 been made during the past century in the natural history of Scan- 

 dinavia. Under such favourable circumstances, geological science 

 may safely expect some light to be thrown even on these obscure 

 questions. 



Note. — The author then, in some remarks appended to his memoir, states 

 that he obtained a line of departure or a base line for his measurements, from 

 the observation of the growth of a fucus (F. vesiculosus^), very abundant on the 

 northern shores, and ranging between high and low water about 0'6 m above 

 the mean height of the water. In this way the observations could be readily 

 made at any time of the tide and with little danger of error. 



In order to obtain the ancient mean level, the re-entering angle of a line of 

 erosion, or the highest point of the edge of a terrace, was taken for the place of 

 admeasurement wherever it was practicable ; but these points are not absolutely 

 correct, and there is necessarily a source of error, the limit of which is stated 

 from some observations made in the neighbouring seas to amount to 1 '5 m ; but 

 M. Bravais considers, that by more accurate and extensive observations a mean 

 might be ascertained. The whole of this correction must of course be deducted 

 from the calculated amount of the last elevation. 



M. Bravais adds, that if at the time when observations of this kind are being 

 made, the amount of erosion at present and at former times could also be re- 

 corded, and the historical data added as to the minimum number of years that 

 have elapsed since the latest elevation, we might perhaps obtain the means of 

 determining an inferior limit of the duration of those periods of repose during 

 which the ancient lines of level have been in the course of formation. 



D. T. A. 



