DESTROYERS OF SUBMERGED WOOD — MURPHY. 221 



no current a strong application of a solution of connnon lime 

 applied in the months of June, July and August, whilst the ex- 

 pelled ova are undergoing development, might prove effective. 



In such places as the Bras d'Or Lakes or in land-locked har- 

 bours where the lime would not be immediately carried away hy 

 a current, the experiment might be worth trying. An applica- 

 tion of a barrel of lime dissolved in about eight or nine barrels of 

 water and poured around the piles of a wharf might be tried, or 

 a stronger solution if considered desirable, or still better, if forced 

 around each pile through a hose and nozzle with an ordinary 

 force pump. 



I conclude with some notes on the effect of current on the 

 ravages of Limnoria, communicated to me in January, 1892, by 

 Mr. W. B. McKenzie, C. E., of the Intercolonial Railway Office, 

 Moncton, N. B. His observations were made on piles of the 

 Intercolonial Railway Bridge across the Narrows of Halifax 

 Harbor, and are as follows : — 



" Hemlock piles driven seven years ago, with bark on, into a 

 hard gravel bottom with boulders, in salt water, 55 ft. in depth, 

 where the tide rises 6 ft. and the surface velocity is 2h miles per 

 hour, were found to be worm-eaten from the surface of the 

 ground upwards about ten feet, as shown on the accompanying 

 photograph (reproduced in Plate II.) No. 1 pile appears not to 

 have entered the ground but probably rested on a fiat boulder 

 No. 2 pile penetrated Ih ft. No. 3 pile penetrated 3f ft. The 

 rate of destruction averages *o of an inch per year, reducing the 

 diameter of pile f„ of an inch per year. As it has heretofore been 

 asserted, and is a generally accepted opinion that the Limnoria 

 works at extreme low water only, or thereabout, the discovery 

 was surprising that, in this case, no damage of any consequence 

 was done at this point, but that its operations were confined to 

 the bottom part of the pile, being greatest at its ground line and 

 decreasing upwards for a distance of about 10 feet. 



" I can only account for this on the hypothesis that the 

 current being about 2| to to 3 miles per hour at the surface, the 

 Limnoria found it easier and more convenient to work down 

 near the bottom, where the current was probably much less. 



