3S2 Dr Coldstream on ike Structure and 



worthy of remark, that some of the Leith Fort piles seem to 

 have been bored from above downwards. This I suppose to 

 have been owing to these having had originally small cavities 

 in their summits, giving lodgement to minute pools of sea-water 

 during the recess of the tide, and thus enabling the borer to con- 

 tinue its work, even within a very short distance of high water- 

 mark. Such piles are hollowed out in the centre above, as well 

 as eaten away round their bases externally. 



I have now adduced a sufficient number of facts to prove 

 that this destructive animal is very abundant on the coasts of 

 Scotland. I have to add, that it occurs also on the English 

 shores, and that Mr Stevenson has witnessed its ravages on the 

 coasts both of France and the Netherlands. Last year, I 

 found it in a small piece of wood, which had apparently been 

 long in the water, thrown ashore in Torbay, Devonshire. 



V. On the purposes which the Limnoria is fitted to serve in the 

 economic of nature- 



Although the destructive agency exerted by this minute ani- 

 mal be forced upon our attention chiefly by its ravages on works 

 of great public utility, and, therefore, cannot at first view be re- 

 garded by us with complacency or admiration ; yet, upon further 

 reflection, we must be convinced, that the purposes which the lim- 

 noria is fitted to serve in the great plan of creation, are such as 

 could be accomplished by no other living creature with which 

 we are acquainted, and that they are calculated to contribute 

 in no small degree to the comfort and well-being of man. Let 

 us consider, for instance, how possible it is that large trees or 

 masses of wood, floated down by rivers, might accumulate on 

 shoals at their mouths to such an extent as materially to dimi- 

 nish the outlet for the waters, which then would rise and over- 

 flow their banks, were it not for the destructive boring of the 

 limnoria. What could not be accomplished by the brute force 

 of any marine animal, and might bafile even the ingenuity and 

 power of man himself, is yet quietly accomplished by the gra- 

 dual but steady operations of a tiny crab. The trees are perfo- 

 rated, and then washed away, and with them the sand and 

 mud which had collected around, and which would speedi- 

 ly have formed an eff*ectual impediment at once to the free ef- 



