THE RHONE FLOODS.
1 Adam Street, Adelphi, 30th June 1856. Sin—Your correspondent "X." doubts my hypothesis as to the source of the Rhone floods being the too rapidly thawing snows. Will he assign any other reason for the occasional floods of late years, Which reach to the mud houses—formerly out of reach—of Lyons, and the droughts which usually succeed ? Be assumes that because Lyons is inundated, therefore Geneva should be inundated else, on account of the narrow outlet; but, if I mis- take not, this narrow outlet, the "blue rushing of the arrowy Rhone," is also a very deep outlet. 'The lake of Geneva is a very large surface, and it can expand greatly without overflowing its banks at the town, though the pressure may greatly increase the volume of water discharged through a given space. It is of the nature of a mountain ravine, which takes no da- mage from the flood which swamps the valley.
There are no doubt, other circumstances at work. All rivers have a ten- dency to raise their beds by deposits. The Mississippi bears large vessels high above the roofs of the 'houses in New Orleans, restrained by artificial banke. The Po is in the same condition, and is a source of constant anxiety to Italian engineers. X. speaks of the Valais, but he forgets the rocks that
arise in the direction of Chanicemi and Mont 'Blanc, and that a moimtainous country provides against floods by natural channels not found in fiat coun- tries. If Switzerland bei as X. asserts, more heavily timbered than before, and that the snows are still covered by trees and vegetable swamps and. bogs -preserved, still it is quite clear that carcumetances are at work not formerly .known, and which wall compel people to build houses of burnt brick in the neighbourhood of Lyons where formerly mud sufficed. If the floods be pm- duced by rain in France, and not by the watershed-of Switzerland, building up high dikes to the Rhone will not help the matter. It is aknown fact that timber is decreasing in the lake districts of the United States by the pre- sence of population, and unless the population of Switzerland be it is-hardly probable that the timber will increase.
I am, Sir, yours faithfully, W. Bitmons ADAMS.
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