S54 FLOATING OF TIMBEK. 



be 80 guided, as to avoid damage to the shore, but to masts, loga 

 and other pieces of timber singly entrusted to the streams, to be 

 conveyed by their currents to sawmill ponds, or to convenient 

 places for collecting them into rafts. The lumbermen usually 

 haul the timber to the banks of the rivers in the winter, and 

 when the spring floods swell the streams and break up the ice, 

 they roll the logs into the water, leaving them to float down to 

 their destination. If the transporting stream is too small to fur- 

 nish a sufficient channel for this rude navigation, it is sometimes 

 dammed up, and the timber collected in the pond thus formed 

 above the dam. When the pond is full, a sluice is opened, or 

 the dam is blown up or otherwise suddenly broken, and the whole 

 mass of lumber above it is hurried down with the roUing flood. 

 Both of these modes of proceeding expose the banks of the 

 rivers employed as channels of flotation to abrasion,* and in some 

 of the American States it has been found necessary to protect, 

 by special legislation, the lands through which they flow from 

 the serious injury sometimes received through the practices I have 

 described.f Switzerland, as might be expected from the phys- 



die Buchen-Wirihschaft, 1863. A. Matiry, Les For its de la Oaule, pp. 73, 74, 

 377, 384. 



Within the last few years, the trunks of many well-grown oaks, in a par- 

 tially decayed condition, have been extracted from bogs in Finland, in dis- 

 tricts where the present spontaneous forest growth is composed wholly of 

 spike-leaved trees. — Blomquist, Catalogue, etc. 



In the ancient forest of Valombrosa, the primitive beeches have been, to a 

 great extent, superseded by firs and other trees of the same genera. 



* Caimi states that "a single flotation in the Valtelline, in 1839, caused 

 damages appraised at $250,000." — Cenni sulla Importama e Coltura deiBosclii, 

 p. 65. 



f Many physicists who have investigated the laws of natural hydraulics 

 maintain that, in consequence of direct obstruction and frictional resistance to 

 the flow of the water of rivers along their banks, there is both an increased 

 rapidity of current and an elevation of the water in the middle of the channel, 

 so that a river presents always a convex surface. Others have thought that 

 the acknowledged greater swiftness of the central current must produce a 

 depression in that part of the stream. The lumbermen affirm that, while 

 rivers are rising, the water is highest in the middle of the channel, and tends 

 to throw floating objects shorewards ; while they axe falling, it is lowest in the 

 middle, and floating objects incline towards the centre. Logs, they say, rolled 

 into the water during the rise, are very apt to lodge on the banks, while those 

 set afloat during the falling of the waters keep in the current, and are carried 



