FLOATING. 385 



oflf stranded logs, or land timber, and be able to move about 

 expeditiously. 



The only difficulty in lower mountain-valleys and level 

 ground, is to come to terms with the riparian owners about sites 

 for the construction of booms, &c. In the higher mountain 

 passes, however, steep precipices often line the banks of narrow 

 gorges, through which the stream passes, and the logs can be 

 controlled by the workmen, only at great risk to their lives. 

 Such gorges are especially common among limestone rocks, and 

 form passes between the higher and lower stages of the valleys, 

 the water falling in a series of cascades among large boulders and 

 masses of rock. The floating wood is constantly sticking in such 

 places, and a whole sweep of timber may thus be stopped. In 

 order to prevent this mischance, the gorges must be made 

 passable, and a pathway is often constructed with wooden 

 galleries supported by numerous iron bars and wooden beams 

 let into the rock, and connected with one another by steps cut 

 in the rocks, and by ladders. 



3. Booms. 



Booms are constructions intended to arrest or divert the passage 

 of all floating wood at a fixed point in a stream. All floating 

 timber is thus stopped or diverted by the boom, and where large 

 sweeps of timber come down, the boom has to resist consider- 

 able pressure and must be very strongly constructed ; its site 

 also should be favourably situated for the purpose in view. 



Booms, therefore, vary from those of the simplest nature to 

 colossal structures costing thousands of pounds. Most of these 

 booms are constructed by ordinary woodcutters or floaters, 

 who from long experience in the work frequently show great 

 ingenuity ; some of them may even be classed as engineers. 

 But for the very reason that the nature of booms depends 

 on local conditions, no constructions are more varied, and 

 hardly any two booms are alike. In the following paragraphs, 

 therefore, some characteristic forms of booms only will be 

 considered. 



(a) Mode of construction. — There are three essential points in 

 the construction of a boom, the supports, the horizontal bars 



VOL. v. C C 



