I9II.] STEVENSON— FORMATION OF COAL BEDS. 535 



Many of those are old trees which had withstood floods for more 

 than a century, others were very young ; but the age mattered nothing, 

 the saphng resisted as well as did the older tree, provided only that 

 it was rooted in material that would not soften during the flood. 

 One great flood had poured over the second bottom in the late sum- 

 mer when the maize had attained its height. But it did not tear the 

 plants from the soil ; pressure against the broad leaves sufficed only 

 to prostrate the plant ; none was removed. 



xA.t the same time, the eft'ect of the flood was shown by trees on 

 the lower bottom, for those 25 or more feet high, if slender, were 

 bent down stream. Those with broad spreading crowns were affected 

 b}- pressure at the surface of the current. No doubt, if the flood 

 had been repeated at intervals of two or three days, not a few of 

 those trees would have been overturned ; but, once overturned against 

 their neighbors, they would tend to protect the others by increasing 

 the density of the mass and so acting as breakwaters to divide the 

 flow. The flood had no effect where the vegetation was dense, the 

 close growth evidently reducing the current to gentle movement. 

 Croppings of peat bogs, i to 3 feet thick, appear at many places in 

 the banks. Such bogs suft"er no injury except by undermining; in 

 which case, a floating log occasionally tears off a piece. 



The floods of the Passaic in New Jersey and of the Susquehanna 

 have been described in several publications. They are more disas- 

 trous than those of the Connecticut, from a pecuniary point of view ; 

 but those rivers in flood are no more effective than the Connecticut 

 in the struggle against vegetation. 



The Potomac river, though of rather rapid fall, flows in a broad 

 shallow channel, an anomaly due in great degree to the relation 

 between its normal stage and its freshets. The flood of June i and 

 2, 1888, the greatest on record, was described briefly by McGee.^^ The 

 height of water at Washington was no greater than during freshets 

 caused by ice jams, but, above the limit of tidal influence, the volume 

 of water and height of rise exceeded any previously recorded. The 



''W J McGee, Tenth Ann. Rep. U. S. Geol. Survey, 1890, "Administra- 

 tive Report," pp. 150-152. 



PROG. AMER. PHIL. SOC. , L. 202 JJ, PRINTED NOV. I5, I9II. 



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