272 SCIENCE PROGRESS 



means of quickening the cycles and greatly increasing the output 

 of an apparatus of a given size. It is convenient to substitute 

 for vessel e two vessels, one for air and one for gas, so 

 as to maintain the combustible constituents separate until 

 they enter the combustion chambers. If the first portion 

 of the out-stroke of the water column is allowed to reject 

 the surplus air and gas back to the sources of supply, then 

 the action throughout the cycle is precisely that described 

 when using the single vessel e, except that a larger proportion 

 of the total energy is absorbed in the compression of air and 

 gas but the excess is given out again during the expansion 

 of the pre-compressed charge in either a or b. The chief 

 advantage arises from the more rapid working, as there is no 

 longer any need to wait for the water level in a or b to fall 

 under the action of gravity when the charge is being taken in. 

 In fact the apparatus becomes practically independent of the 

 water level on the supply side. The 1,000 h.p. Humphrey 

 pump now under construction in Germany is designed to 

 operate with pre-compression of the charge, the result being 

 that the dimensions are very moderate and the pump itself 

 occupies no more space than a 1,000 h.p. tandem gas engine. 



Sufficient has been said to show that the variety of types of 

 the Humphrey pump may be multiplied indefinitely whilst still 

 maintaining the same principles of operation; it may be men- 

 tioned also that pumps have been designed in which, instead of 

 a sudden explosion, the combustible mixture is injected and 

 burnt at approximately constant pressure. Humphrey pumps 

 have been successfully operated on producer gas, coal gas, 

 water gas, petrol and paraffin and patents have been taken out 

 for designs specially suitable for use with crude oil as fuel ; but 

 space does not permit of these modifications being described, 

 more especially as this article will be concluded by a description 

 of the Humphrey Air Compressor. 



If the column of water oscillating in the play pipe of a 

 Humphrey pump is used as a water piston and caused to rise 

 and fall in an air vessel fitted with suitable valves for the inlet 

 and outlet of air, the combination constitutes an air compressor 

 of a very efficient type and promising many advantages. Let 

 us take the case of a single-barrel pump and a single air vessel, 

 as illustrated in fig. 7. a is the ordinary pump chamber and c 

 the air compressor chamber; we may call these for con- 



