44 STATE BOARD OF FORESTRY. 



soned gray, red and sugar gum timbers are moderately durable and 

 should give longer service than blue gum. Sugar gum is probably the 

 best eucalypt for tie production. 



Mini Timbers. Blue and sugar gum have been used with success in 

 limbering mines near Escondido. The gum timber has been found 

 superior to any other obtainable there. Few of the timbers have 

 decayed, although the mines are flooded during a part of each year. 

 . Difference in value of the two species has not yet become apparent, but 

 it is probable the sugar gum will prove superior, as it excels blue gum 

 in both strength and durability. 



Wharf Piling. The problem of maintaining wharves has become an 

 important one on the Pacific coast. Not only are the best pile timbers 

 very expensive, but they will not resist the attacks of the teredo and 

 limnoria and have to be replaced continually. 



Both the teredo and limnoria are troublesome all along the Pacific 

 coast, being carried from port to port by the shipping. The teredo 

 attacks the piling at the ground line, under water, and burrows cham- 

 bers through the wood. When the piling is unprotected, this source 

 of injury is generally negligible, for the timbers are more speedily eaten 

 off at the water line by the limnoria. The limnoria have no natural 

 enemies in American waters to decimate their numbers, hence they are 

 constantly increasing and becoming more troublesome. Their attacks 

 are particularly severe in the warm waters of the southern ports and 

 in sheltered harbors. 



In an attempt to maintain durable wharves, experiments have been 

 made with costly iron and cement piles, but the lower cost and greater 

 ease of setting keeps the wooden pile in favor. Various expensive treat- 

 ing and sheathing experiments have been tried, but preservative processes 

 have failed so far to check the borers. Limnoria will not attack wood 

 which is coated with sand. This fact has been taken advantage of to 

 defeat them by applying a rough cement wash to the exposed surface 

 of the piles. This coating not being elastic, however, fails to prevent 

 the limnoria from entering at season checks and continuing their work 

 under the cement covering. Pile timbers are generally creosoted or 

 oiled, and often wrapped and battened, to increase their period of 

 service, but limnorias attack even creosoted wood. When untreated, 

 piles are generally set unpeeled, as the borers do not work while the 

 bark remains. 



Aside from its use for fuel, gum timber has been most extensivelv 

 used for piling. After extended trial the blue gum pile has been 

 determined the best in use on the Pacific coast. Whenever it can be 

 obtained, contractors and wharf managers discriminate in its favor. 



