152 Pruccedings of the Roijal Fliysiccd Society, 



metal pipes till in 1879 a correspondence on the subject of 

 " Intelligence in Brutes " took place in the columns of 

 Nature, when the matter was referred to in the letters of 

 six or seven different writers. In these communications a 

 number of instances — none of them, however, exce]3tionally 

 interesting — are given, and several opinions expressed re- 

 specting the purpose for which the rats gnaw the pipes. 

 Some think it is done simply to get at the water ; others, 

 that it is because the pipes are in the way of their tunnelling 

 operations ; others, again, that it is merely for the love of 

 gnawing. One writer considers the rats find out that pipes 

 contain water through their cutting them, in the first instance, 

 as obstructions. Mr Darwin thinks they hear the water 

 trickling. In Edinburgh and some other towns they must 

 often hear the water rushing. It may sometimes be the case 

 that a very slight crack or " sweating " of a pipe — yielding at 

 intervals only a mere drop of water — tempts rats to gnaw a 

 hole in the lead in order to get a proper draught. A corre- 

 spondent of Nature, relates an instance of rats gnawing the 

 bullets in Martini- Henry rifle cartridges, in order, no doubt, 

 to get at the grease. 



The most extraordinary specimen of a gnawed pipe which 

 I have seen, is one which was given to Professor Archer 

 in September 1877 by Mr J. J. M' Andrew of Lukesland, Ivy 

 Bridge, Devon. It was part of a vertical pipe for pumping 

 water from the fresh-water tank in the bottom of a ship to 

 the deck. The rats, in their desperation to get at the water, 

 have bitten it away by degrees till they have made a hole 13 

 inches in length by about 1 inch of average breadth. In 

 other words, they have completely removed with their 

 teeth 13 square inches of lead, y\ of an inch thick. Here 

 is another example of a gnawed waste-pipe, for which I 

 am indebted to Dr Grierson of Thornhill. It has two holes 

 in it, the larger of which measures about 8 square inches, 

 but in this case the lead is barely \ of an inch thick. A 

 very similar example has been sent to me by Mr Nucator, 

 plumber, Dundee, who has also told me of one or two cases 

 where great annoyance and trouble have been caused through 

 waste-pipes from water-closets having been gnawed by rats 



