[ 193 3 



XXX. Account of the improved Pump invented by Mr. 

 Robertson Buchanan, Engineer, No. 57, Piccadilly. 



X HE many fatal accidents which happened to (hips from 

 the choking of their pumps, made it an important object, in 

 naval affairs, to find fome machine for freeing (liips from 

 water not liable to fo dangerous a defect. The chain pump, 

 having been found lead exceptionable in this reflect, was 

 adopted in the Brititfi navy ; but, as Mr. Townfend obferves, 

 <e the chain pump itfelf is not free from imperfections. If - 

 the valves are not well fitted to the cylinder, through which 

 they move, much water will fall back ; if they are well fitted, 

 the friction of many valves muff be confiderable, befides the 

 friction of the chain round the fprocket wheels, and of the 

 wheels themfelves." To which may be added the great wear 

 of leathers *, and the difadvantage which attends the furging 

 and breaking of the chain. " The preference, therefore, 

 which has been given to chain pumps over thofe which work 

 by the preffure of the atmofphere, muft have arifen from this 

 one circumftance, that they have been found lefs liable to 

 choke. 



" In point of friction, of coolnefs, and of cheapnefs, the. 

 fucking pump has fo evidently the advantage over the chain 

 pump, that it will not fail to gain the preference whenever it 

 fhall be no longer liable to be choked with gravel and with, 

 chips f." 



Buchanan's pump, which, like the common pump, acts 

 by the preffure of the atmofphere, is not liable to the defects 

 incident to other pumps upon that principle, being effentially 

 different from any now in ufe. 



The conitruction of this pump will be eafily underflood 

 from the following fhort defcription: 



Fig. 1. (Plate III.) is a vertical fection of the pump, as 

 made of metal, in which A is the fuction -piece, as it is com- 

 monly called; B, the inner valve; C, the outer valve. The 

 valves are of the kind called clack valves ; their hinges are 

 generally made of metal, as being more durable than leather; 

 and, requiring no boxes, are peculiarly fimple in their con- 

 ftruction. D, the working barrel ; E, the pifton ; G, the 

 fpdut. 



Fig. 2. is a fection, by the line a b, of fig. I, mowing how 



* Sec Captain Inglefield's Narrative. 

 f Townfcnd's Journev, vol. i. p. 171. 



Vol. X. N the 



Phil. Mag. No. 39. 

 Augiift 1 80 1. 



