THE FORMATION OF COAL. 87 



tratiou of water in the lower parts, where the pressure would 

 be greatest, and thus the upright or oblique position of 

 many of the floating trunks would be maintained till they 

 absorbed sufficient water to sink altogether. 



It is generally assumed that fpssil trees which are found 

 in an upright position haye grown on the spot where they 

 are found. The facts I have stated show that this infer- 

 ence is by no means necessary, not even when the roots are 

 attached and some soil is found among them. In order to 

 account for the other surroundings of these fossil trees a 

 very violent hypothesis is commonly made, viz., that the 

 soil on which they grew sank down some hundreds of feet 

 without disturbing them. This demands a great strain 

 upon the scientific imagination, even in reference to the 

 few cases where the trees stand perpendicular. As the 

 majority slope considerably the difficulty is still greater. I 

 shall presently show how trees like those immersed in 

 Aachensee may have become, and are now becoming, im- 

 bedded in rocks similar to those of the Coal Measures. 



In the course of subsequent excursions on the fjords of 

 Norway I was reminded of the sub-aqueous forest of the 

 Aachensee, and of the paper which I read at the British 

 Association meeting of 1865, of which the above is an ab- 

 stract not by again seeing such a deposit under water, 

 for none of the fjords approach the singular transparency 

 of the lake, but by a repetition on a far larger scale of the 

 downward strips of denuded forest ground. Here, in Nor- 

 way, their magnitude justifies me in describing them as 

 vegetable avalanches. They may be seen on the Sognef jord, 

 and especially on those terminal branches of this great 

 estuary, of which the steep slopes are well wooded. But 

 the most remarkable display that I have seen was in the 

 course of the magnificent, and now easily made, journey up 

 the Storfjord and its extension and branches, the Slyngs- 

 fjord, Sunelvsfjord, Nordalsfjord, and Geirangerfjord. 

 Here these avalanches of trees, with their accompaniment 

 of fragments of rock, are of such frequent occurrence that 

 sites of the farm-houses are commonly selected with refer- 

 ence to possible shelter from their ravages. In spite of this 

 they do not always escape. In the October previous to my 



