88 IMPROVED FISHERY HARBOUR ACCOMMODATION 



The weak point of masonry is that it lacks continuity, 

 whereas timber possesses this in an eminent degree. 



Timber is very largely used now in construction, 

 as well as an adjunct, in many forms and features of 

 harbour work ; and in the form of piling, either with stone 

 within and surrounding the piles, or without, or in boxes 

 rilled with stone, is often met with at the present day. 

 The Romans frequently used this latter method. Mr. 

 Stevenson not only mentions this, but gives a long extract 

 from a contract in Latin, between the Abbots of Arbroath 

 and the Burgesses, dating 450 years since, mentioning the 

 stone-filled timber chest method in the construction of 

 harbour works. 



DESTRUCTION OF TIMBER BY WORMS. 



The writer has adverted already to this subject, but 

 some further observations may not possibly be thought out 

 of place here. The three great mischief-makers are the 

 Teredo navalis, the Limnoria terebrans, and the Chelura 

 terebrans. The Teredo burrows internally, the Limnorics 

 plough away on the exterior, in some places at the rate 

 of an inch inwards per annum ; and between the three 

 timber has a very short duration, becoming burrowed 

 and honeycombed to that degree, that it actually falls to 

 pieces. 



The writer has known three flights of wooden steps 

 eaten in nine years, and jetties requiring rebuilding. It 

 was formerly thought that the damage between low and 

 high-water marks was not considerable, but extended 

 experience has proved that the worms work at all heights 

 between high and low water, and under low-water level 

 until the pile enters the sand. Mr. R. Stevenson's experi- 



