186 report — 1865. 



per minute, showing an expenditure of air equal to 3 horse-power. The machines 

 at Blaina Ironworks, South Wales, were working in coal which the men refused 

 to work, and which, though opened out, has not been touched for years, and hole 

 at the rate of 8 yards per hour, to a depth of 3 feet. The machine, when woiked 

 with the outward cut and self-propelling motion, will exceed this quantity con- 

 siderably. 



On some Developments of and Improvements in Giffard's Injector. 



By J. Robinson. 

 Having referred to the difference of opinion existing among engineers as to this, 

 which had been called by the President a somewhat paradoxical instrument, the 

 author described the action of the injector to be as follows : — Steam was taken from 

 the steam space of any boiler by means of the injector, the water supply was brought 

 into contact with the steam current, and the result in the shape of hot water was 

 passed into the water space of the boiler. The question was, how, having an equal 

 pressure on all parts of the boiler, did a fluid not only pass in the shape of a current 

 from one part to another, but at the same time carry with it another fluid exposed 

 to atmospheric pressure only ? The author propounded the following explanation 

 of the instrument : — Advantage is taken of the superior velocity at which a steam 

 current issues from a boiler, over that of a water current issuing from a boiler at 

 the same pressure. These velocities are assumed to bear an exact proportion to 

 the densities of the two fluids. The steam current having but a small amount of 

 momentum, the water supply is brought into contact with it, and two results fol- 

 low : first, the steam current is incorporated with the water current by the con- 

 densation of the former; secondly, an amount of the velocity of the steam current is 

 imparted to the water current in the proportion of the quantities of each which are 

 brought together in the combined jet. As the weight of steam issuing from an 

 opening is exactly equal to the weight of water which would, under the like pressure, 

 issue from the same opening in the same time, the area for the admission of steam 

 to the combining chamber is made greater than the area of the pipe which receives 

 the condensed jet for transmission to the boiler, as otherwise the amount of velocity 

 imparted to the water current would not be sufficient to overcome the velocity of 

 the resisting current from the boiler. The combination of the foregoing principles 

 and arrangements in the injector is so effective that, steam at a pressure of 30 lbs. 

 above the atmosphere, water can be forced into a boiler containing steam of very 

 nearly double that pressure. Having described the construction of the injector, 

 the paper pointed out the importance of an apparatus capable of supplying water to 

 steam boilers without motion of any of its parts, and independently of the engine 

 connected with it. It had proved almost essential to some particular arrange- 

 ments of boilers and engines. For locomotives, the advantage had been very con- 

 siderable, inasmuch as it was most important that the machinery of engines run- 

 ning at such high velocity should be free from the apparatus and repairs necessary 

 when their boilers were fed by pumps worked by the engine. The advantage also 

 was obtained by feeding the boiler while the locomotive was at rest, either in the 

 station, or during its retention in a siding waiting for the line to be cleared. For 

 this purpose 5230 of the injectors had been manufactured in this country. For 

 stationary boilers the injector had been found convenient, because of the saving of 

 the pipes and other communication from the boiler to the engine-room, the sup- 

 pression of the pumps and the parts of the engine necessary to work them, and the 

 advantage of being able to fill up the boilers during meal hours, and at other times 

 when the engine was stopped. For this purpose 3816 had been made in this country. 

 For marine boilers the apparatus was most convenient, since it answered generally 

 the purpose both of the main engine pumps and of the donkey pumps, and brought 

 the control of the feeding-apparatus within reach of the stokers, without reference 

 to the engine-room, and without the noise and complication of the donkey pump. 

 In a simple form, and also in the ordinary injector arrangement, the principle had 

 been applied for raising water from mines and wells, the inducement being the 

 cheapness and simplicity of the apparatus, and the small space and easy manipula- 

 tion required. The paper proceeded to describe in detail improvements which had 



