Mr Matheson on. a new mode of constructing Harbours. 83 



supposition that the smaller number is the correct one, though 

 Mr Dalton appears still to consider it doubtful. Dr Wol- 

 lastou's equivalent for copper was exactly four times that of 

 oxygen. In silver we are not entitled to draw a similar conclu- 

 sion, and there is no analysis of an oxide or salt of silver 

 which would entitle us to consider its atom half the weight 

 Mr Dalton has it. Hence we are reduced to the alternative, 

 that there is either another oxide of silver containing a larger 

 proportion of oxygen than the one commonly known, and which 

 has never yet been detected by chemists, or this metal must 

 stand an exception to a law which holds so remarkably with 

 the others. If, as I expect, the common oxide of silver will 

 prove to be a sub-oxide, we shall here have an exemplification 

 of the unexpected assistance which abstruse inquiries often lend 

 to those branches of science where it was least anticipated. 

 lith May 1831. 



Aut. VIII. — Observations on a new mode of constructing Har- 

 bours. By William Matheson, Civil-Engineer. Com- 

 municated by the Author.* 



The importance of good harbours to a mercantile country will be 

 universally admitted, and the commercial eminence great Bri- 

 tain has attained, has naturally directed the attention of per- 

 sons interested, in the extension of her trade, to the improve- 

 ment of the surrounding harbours ; and perhaps in no way has 

 the skill and ingenuity of engineers been more extensively 

 employed, or more usefully directed. Many great works have 

 been executed at an enormous expence, and some of them have 

 succeeded more or less, to the expectation of the parties. 



The erection of works within tide mark must always be 

 attended with trouble and additional expence, and it is the more 

 to be lamented after such expensive operations have been carried 

 into effect, that the whole benefit <>f them should be frustrated 

 by some unforseen circumstance, which has too frequently hap- 

 pened in such operations. 



Of these latent difficulties, none has had a more powerful in- 

 fluence than the tendency of the tide, or the motion of the 



* Read before the Royal Si ;i tj of Edin, i 1 - 31 



