62 
PRESERVATION OF PILING AGAINST MARINE 
BORERS. 
The length of service of piles in wharfs and' other marine struc- 
tures is greatly shortened by the attack of marine borers, or ship- 
worms. A method of protection, both efficient and cheap, is much 
needed, the more so because the timbers best suited for piling are 
becoming very scare and are increasing rapidly in price. 
Marine borers are found as far north as Maine and Alaska, 
though they are more numerous and destructive in the warmer 
waters farther south. Since they require only a small exposed 
surface in order to gain entrance and completely destroy a pile, 
any effective means of preservation must protect the wood from 
high-water mark to a point in the mud below which the borers 
do not go. 
A number of excellent methods have been devised for protecting 
piling by external coatings or sheathings, any of which, properly 
applied, will increase the life of the pile. Three factors which de- 
crease their efficiency are the corroding action of salt water, the 
wash of the waves which injures and often breaks the casing, and 
the dangers from floating timbers and debris. Thick iron cases 
resist damage from these sources for a long period, but they are 
very expensive. , 
The injection of preservatives through holes bored in the top 
of the pile, or near the mud line, has failed to secure a distribution 
sufficient to adequately protect the outer layer of wood. All 
soluble salts have also shown a tendency to leach out when ex- 
posed to salt water. Impregnation with creosote, a coal-tar pro- 
duct, has usually proved' highly efficient with suitable kinds of tim- 
ber properly prepared when a sufficient quantity of good creosote 
is used. 
The principal timbers used for piling are longleaf, shortleaf, 
and loblolly pine, and white and red oak on the Atlantic coast and 
Gulf of Mexico, and Douglas fir on the Pacific coast. Spruce, 
redwood, cedar, cypress, eucalyptus and palmetto are used locally. 
All of these woods with the exception of palmetto are subject to 
damage by borers. Hardness is not a complete barrier to their 
attack, although boring is probably slow in dense woods. South- 
ern pine and oak can be impregnated with creosote, and this prom- 
ises to be one of the most efficient means of resisting the borers. 
Circular 128, just issued by the Forest Service, gives a detailed 
description of the most important marine borers and their habits, 
together with a discussion of the different forms of mechanical 
devices in use for the protection of piling and of protection by 
chemical preservatives. This publication will be sent free upon 
application to the Forester, Department of Agriculture, Washing- 
ton, D. C. 
