168 OF THE POWER OF STEAM, [SECT. iv. 



Dr. Ure's 1 experiments were also made by boiling different kinds of water, and 

 measuring the result by a pneumatic apparatus, and at the temperature of about 

 55: the proportions of gaseous matter in 100 volumes of water were found to be 

 as stated below. 



Canal water (in winter) ..... 2'67 per cent. 

 Filtered river water supplied to Glasgow by the 



pipes of the Cranstonhill Water Company . 2 '52 



Filtered river water from the pipes of the Glasgow 



Water Company ..... 2'50 



Water from the river Clyde, when swollen by 



winter rains ...... 2'80 - 



It cannot be supposed that in these experiments the whole of the gaseous 

 contents of the water were obtained, but assuming that two-thirds of the total 

 gaseous contents are obtained by boiling, the quantity will vary from 3'75 to 4'2 

 per cent; and therefore, for river and canal water, we may assume that water 

 contains 5 per cent of air, or w of its volume. 



The action of pumping it appears, from Dr. Ure's researches, expels a portion of 

 air from water. 



346. The preceding articles afford us data sufficiently accurate for the general 

 purposes of inquiry, and in such inquiry we may suppose that, at the mean tem- 

 perature and pressure, 



River or canal water contains ?V~I 



c . n , f ot its volume of gaseous matter. 



Spring or well water T V J 



347. The quantity of water which enters into a steam engine will all of it give 

 out nearly the whole quantity of air it contains ; therefore, calculating the volume 

 of water used for steam at each stroke of the engine, and adding to it that used 

 for injection in the same time, we have 2*0 part for the volume of air at 60 ; 

 but in the condenser it will be of the temperature of the hot well, or about 120; 

 and the quantity the air expands by this increase of temperature being calculated, 

 (see art, 119.) the bulk is found to be 5'6 per cent of that of the water, or iV of the 

 bulk of the water nearly. 



348. Let the injection water added to the water of the condensed steam be 

 of the volume of the cylinder for each stroke, then A of yV, or -gw of the cylinder's 

 volume of air, would accumulate at each stroke if there were no air pump. Now a 

 cubic foot of air mixes with a cubic foot of steam, when both are of the same force 



1 Quarterly Journal of Science, vol. xxi. p. 71. 



