112 Mr Stewart on the Causes of Obstruction in 



Report by Mr Dunn. 



Mr Stewart Hepburn is correct in stating that fluids hold 

 a quantity of air in solution, or mechanically combined with 

 them, although I am afraid his proof, deduced from the filling 

 of a barometer-tube, will not hold good, as indeed the expression 

 he makes use of, " unprepared mercury," indicates itself. Mr 

 Hepburn is perhaps not aware, that a very large proportion of all 

 the barometers made are filled simply by pouring the mercury 

 into the tube. It is only the more carefully made ones that 

 have the mercury boiled in the tube. I would find no difficulty 

 in fining a tube either to produce the effect or not, as I had a 

 mind, with the same mercury. 



Mr Hepburn's paper contains many valuable hints as to 'the 

 causes of the obstruction to the flow of water in pipes which, 

 although not new, are highly'valuable and by far too little known. 

 There is a very remarkable similarity betwixt Mr Hepburn's 

 invention and one submitted to the Edinburgh Water Company, 

 or Magistrates of Edinburgh, by Mr Hunter of Thurston, in 

 1820, where Mr Hunter suggests a double air-box, precisely 

 the same as Mr Hepburn's, to be applied to a syphon to rise 

 over the height of George Street, instead of tunnelling. It is, 

 however, I think certain, that the idea was original to both, and 

 aflTords a strong presumptive proof, not only of its being desir- 

 able and useful, but also that it is the best way of effecting the 

 object in view. Upon the whole, I think Mr Stewart Hepburn 

 deserves the best thanks of the Society for his ingenious, and I 

 will say, notwithstanding the remarks I have made above, ori- 

 ginal paper. I should have said that Mr Hunter proposed to 

 open his boxes by stop-cocks. 



Report by Mr George Buchanan. 



COCKBURMSFATH NEAR DUNBAR, 



22d April \SM. 

 In regard to Mr Hepburn's paper, I have not had time to 

 get a regular report completed, but sent you the paper this 

 morning, in which there is a draft of report, and also notes by 

 Mr Dunn. In addition, I would make the following remarks : — 

 Mr Hepburn's paper I consider an ingenious and well written 



