134 SCIENCE IN SHORT CHAPTERS. 



stripped of branches, others with only a few of the larger 

 branches remaining. The roots of all these are more or less 

 buried, and they present the appearance of having grown where 

 they stand. Other trunks were leaning at various angles and 

 partly buried, some trunks and many branches lying down. 



On diving I found the bottom to consist of a loamy powder 

 of gray color, speckled with black particles of vegetable matter 

 thin scaly fragments of bark and leaves. I brought up several 

 twigs and small branches, and with considerable difficulty, after 

 a succession of immersions, succeeded in raising a branch 

 about as thick as my arm and about eight feet long, above 

 three fourths of which was buried, and only the end above 

 ground in the water. My object was to examine the condition 

 of the buried and immersed wood, and I selected this as the 

 oldest piece I could reach. 



I found the wood very dark, the bark entirely gone, and the 

 annual layers curiously loosened and separable from each other, 

 like successive rings of bark. This continued till I had 

 stripped the stick to about half of its original thickness, when 

 it became too compact to yield to further stripping. 



This structure apparently results from the easy decomposition 

 of the remains of the original cambium of each year, and may 

 explain the curious fact that so many specimens of fossilized 

 wood exhibit the original structure of the stem, although all 

 the vegetable matter has been displaced by mineral substances. 

 If this stem had been immersed in water capable of precipitat- 

 ing or depositing mineral matter in very small interstices, the 

 deposit would have filled up the vacant spaces between these 

 rings of wood as the slow decomposition of the vegetable 

 matter proceeded. At a later period, as the more compact 

 wood became decomposed, it would be substituted by a further 

 deposit, and thus concentric strata would be formed, present- 

 ing a mimic counterpart of the vegetable structure. 



The stick examined appeared to be a branch of oak, and was 

 so fully saturated with water that it sunk rapidly upon being 

 released. 



On looking around, the origin of this sub-aqueous forest was 

 obvious enough. Here and there the steep wooded slopes 

 above the lake were broken by long alleys or downward strips 

 of denuded ground, where storm torrents, or some such agency, 

 had cleared away the trees and swept most of them into the 

 lake. A few uprooted trees lying at the sides of these bare 

 alleys told the story plainly enough. Most of these had a 



