48 THE ZOOLOGIST. 
already mentioned, it is effectually kept out by studding the 
surface of the piles with large-headed iron nails (scupper-nails), 
the oxidation of which in the sea-water rapidly impregnates the 
surface to a degree distasteful to the creatures. In the case of 
wrecks it is, however, observable that their borings closely 
approach iron bolts, so that ferruginous wood is not always 
shunned. At Devonport Dockyard the most approved method 
of warding off the attacks of Limnoria is to use good Memel 
timber (fir) thoroughly impregnated with creosote, this absorbent 
wood taking in about ten pounds to the square foot. The wood 
is well dried and warmed before being treated. 
This habit of penetrating wood is unquestionably a very 
ancient one with Limnoria, but within comparatively recent 
years another taste has developed itself, viz. that of perforating 
the protecting envelopes and gutta-percha in which submarine 
telegraph-cables are sheathed. This habit is no less disastrous 
than the former, for by exposing the wires their insulation is 
interfered with, and the cable has to be raised for repairs. Con- 
siderable doubt seems to exist in regard to the form which is thus 
so troublesome to telegraphic engineers ; indeed, it is a prevalent 
impression that annelids cause the mischief. Thus, amongst 
others, the late Dr. Carpenter forwarded Nereis pelagica, a 
common annelid, which like Nereilepas has the habit of dwelling 
in holes made by various borers, as the depredator in the case of 
a Spanish cable. Dr. Gwyn Jeffreys and Sir John Murray sent 
examples of others, including the French Atlantic cable from 
a depth of thirteen hundred fathoms. In all these Limnoria or 
Xylophaga appeared to be the cause of the faults, the repair of 
which is often a costly undertaking. Thus Mr. Andrews,* who 
found Limnoria in the gutta-percha coating of the submarine 
cable between Holyhead and Ireland, observes that a loss to the 
company of no less than £10,000 was eventually caused by this 
diminutive yet destructive crustacean. It would appear, there- 
fore, that the views of Dr. Wallich,+t who thought that “if any 
material exists, the characters of which are so thoroughly dis- 
similar from those of any substance known to occur at the 
bottom of the sea as to render it highly improbable that such 
** Quart. Journ. Micros. Se. (ii.), 15, p. 332. 
+ Ann. Nat. Hist. 3rd ser. (8), p. 58, 1861. 
