1820.] hy the Aid of Atmospheric Pressure. 269 



the urethra may allow to pass, and which are not impeded by- 

 adhesion. I propose to eft'ect this by means of a tube, or canula, 

 so constructed as to allow an exhausted receiver of a portable 

 size to be fixed to it, having its stop-cock to regulate the pressure ; 

 through this canula the calculus may be searched for, and when 

 in contact with it, and the power of the vacuum apphed to it, 

 the powerful suction so excited would, it is presumed, be suffi- 

 cient to draw the attached calculus forward as far as the previous 

 enlargement would allow ; and, according to the size uf the 

 stone, either draw it quite out, or at least so far on in the passage 

 as to be within the reach of a simple operation.* As the end 

 of the proposed instrument must accomodate itself to all surfaces, 

 rough as well as smooth, the having it so formed as best to 

 answer the purpose will be a great desideratum : the body of the 

 canula ought probably to be metallic, but its end or lower termi- 

 nation may be formed of the elastic gum, or some substance of 

 that nature, and in shape and structure perhaps imitative of some 

 processes to be found in the animal kingdom where suction is 

 produced by muscular action. 



A surgeon of eminence in London some time since succeeded 

 in removing a small calculus (said to be of the size of a small 

 walnut) from the bladder of a gentleman, by the following 

 method: he made an opening from the perineum into the membra- 

 nous part of the urethra, and after enlarging the passage with 

 the dilator, he reached and extracted the stone with the common 

 stone forceps. The wound soon healed, nor did the dilatation 

 occasion much pain or other inconvenience. Besides the case 

 of regularly formed calculi, might not the instrument now pro- 

 posed be used also in removing loose granular concretions 

 lodged in the bladder ? In some cases, might it not with advan- 

 tage be substituted for the forceps, especially when they are to 

 act through a long and narrow passage? Might not an instru- 

 ment formed on this principle be used for drawing away aqueous 

 fluid, or pus, situated in parts remote from the surface ? 



Philotecnous. 



Article III. 



Letter from Robert Stevenson, Civil Engineer, to Prof. Thomson, 

 &ic. 3jc. relative to Bonaparte's Fly Bridge on the Scheldt at 

 Antwerp. (With a Plate.) 



I TAKE this opportunity of communicating some observations 

 from my note book, when lately at Antwerp, on a tour through 



• It seems possible, and with mucli advantage, if it could be done, to join toge- 

 ther tile two instruments; in that case when in use, the attached calculus would 

 follow so closely in the wake of the bulb of the dilator as to pass before the 

 dilated parts could close upon it, and a less force be sufficient to move it along. 



