100 Mr Stewart on the Causes of Obstruction in 



that during the long period which has elapsed since the com- 

 mencement of the modern polar expeditions, I have never before 

 j)ut forward publicly any of the present statements. Had I in- 

 deed seen fit to have urged any claim to public consideration, 

 on the grounds kindly mentioned by Sir John Ross, or any de- 

 sire of public acknowledgment so generously suggested in the 

 Edinburgh Review, I might, perhaps, have founded a plea 

 on the above and other grounds ; and had I been disposed 

 to complain of a want of consideration on the part of those 

 who availed themselves, without acknowledgment, of some of 

 my suggestions ; or of those in public offices under Govern- 

 ment, who put me to considerable expenses by two journeys to 

 London on the pubhc service, perhaps a case could have been 

 made out, such as to have excited a feeling with the public, in 

 some degree corresponding to that indicated in the two iriend- 

 ly publications referred to, that I had not been dealt with gene- 

 rously. 



On the Causes of Obstruction in Water-pipes and Syphons from 

 Disengaged Air ; and on the Construction of a Hydraulic 

 Aii'-extractor for Removing them, (With a Model and 

 Drawing.) By J. Stewart Hepburn, Esq. of Colquhalzie, 

 Mem. Soc. Arts.* 



Colquhalzie (by Crieff), 

 Sl^» Qth December 1833. 



I BEG leave to submit to the Directors of the Society of Arts 

 the accompanying paper on the obstruction of water-pipes by 

 air, and the means of removing it. Should the subject be one 

 which they choose to entertain, and the manner of treating it 

 appear worthy of their notice, I shall forward to you a model of 

 the proposed apparatus, and a description of the means of giving 

 it a self-acting power. 



It may be proper to mention, that the circumstance which 

 gave occasion to it was my observing that the London Society 

 of Arts had, seme years ago, given a premium to Mr Cowan for 

 the application to the syphon of a single air-vessel, from which 



• Read before the Society of Arts, 5th February 1834. 



