for compressing Gases or other elastic Fluids. 1 3 



pected from it, I take the earliest opportunity of submitting 

 it to your notice. 



The original idea is due to Mr. David Gordon of the Lon- 

 don Portable Gas Establishment, who published his views on 

 the subject some time back in the Repertory of Arts, — though 

 I believe this is the first pump of the sort that has ever been 

 made. I am yours, &c. 



Feb. 18, 1824. Samuel Seaward. 



In consequence of the general use to which gas is likely 

 to be brought when highly compressed, it becomes important 

 to ascertain the best method of reducing it to that state, so 

 that it shall be most useful and advantageous to the public. 



The present method of compressing gas is attended with a 

 great many disadvantages : these principally consist of a con- 

 siderable loss of gas during the operation of compression, an 

 immense loss of power in consequence of the gas not being 

 completely forced out of the pump barrel, and the excessive 

 wear and tear of the machinery employed therein. 



The pump that has hitherto been used for this purpose 

 consists of a barrel well bored out, open at one end (as A, 

 fig. 1, Plate I.), with the two valves c and d at the other 

 end; and the solid piston B working therein. This is, per- 

 haps, the best possible arrangement of the piston pump, and 

 is the one adopted by some of the first engineers and machi- 

 nists. 



Now, in the using of this pump it is impossible that the 

 piston can be worked so close as to strike the bottom : there 

 must be some space for clearance, otherwise there would be 

 great danger of damaging the valves, or doing other mischief. 

 Say, in a pump of 12-inch stroke and 5 inches diameter, the 

 spaces allowed between the bottom of the piston and the bot- 

 tom of the pump shall be one-eighth of an inch, which is no 

 great deal; now as the operation of compression goes on, this 

 space will be gradually increased, and when the gas arrives at 

 a pressure of 30 atmospheres, or 450 lbs. upon the square inch 

 (which is the average pressure employed by the Portable Gas 

 Company), there will then be the enormous weight of 9000 lbs. 

 acting against the bottom of the barrel and the piston, which 

 will naturally cause them to recede the one from the other; 

 and from the actual spring of the cranks, the looseness and 

 wear of bearings, spring of the connecting rods and cross- 

 heads, and even of the bottom of the pump itself, we may 

 fairly conclude that under this great pressure the piston does 

 not come within one quarter of an inch of the bottom ; con- 

 sequently there remains that quantity of gas under the great 



pressure 



