2.38 
Iron , 
reference to the temperature of the surrounding air, and m 
there is no method likely to be devised where heat would 
not be generated by the action of the particles of air upon 
each other* When the bulb of a thermometer is held in 
the middle of the current of blast, as it issues from the 
discharging- pipe, a temperature is indicated as much low- 
er than the temperature of the surrounding air, as the tem- 
perature of the cylinder was higher ; and it is most pro- 
bable that a much lower degree would be obtained, were 
it not for the previous expression of some heat in the blow- 
ing-cylinder. Upon the whole, I think, the quality of the 
air obtained in this way of blowing uniformly, most fit for 
combustion, provided the numerous pauses and irregu- 
larities of the current of air were done away. 
Air forced into the furnace under water pressure always 
contains a considerable portion of moistrue ; the blast of 
course is colder, as it issues from the discharging-pipe. 
The temperature differs so much from that of the external 
air as to sink the thermometer from 54° down to 28° and i 
30°. Such effects are produced by air coming into com 
tact with water, that, although the temperature of the at- 
mosphere is 60, 65, to 70, yet the blast at the orifice sel- 
dom rises above 38 : the cold produced in this manner is 
much increased if the air is surcharged with so much wa- 
ter as to be visible in the state of a fine spray. The lead- 
ing feature, therefore, of the water- vault, as to its effects 
upon the quality of the air, seems to indicate an almost 
uniform degree of temperature in the blast : this can only 
be occasioned by the warm air in summer taking up a 
greater portion of the water in solution, the escape of 
which at a small orifice, and under a great degree of com- 
pression, produces the very great depression of the ther- 
mometer. I have already hinted at the bad effects pro- 
duced by moist blasts, and shall, in a proper 
.minute! v atttend to them. 
place, more 
I 
