19 
stone in much the same manner as I had obtained before 
with the water. 
This difference in the results on the two occasions was at 
once explained by the different states of the air, for on the 
first occasion it had been cold and dry, whereas on the 
second it was warm and saturated. With the dry air the 
ether spray reduced the temperature so far below 32° that 
the particles of ice did not freeze together — the force of im- 
pact was not sufficient to cause them to thaw in the first 
instance, and hence the water spray was necessary to keep 
this temperature from falling too low — whereas with the 
warm saturated air the ether did not reduce the temperature 
of the air and the vapour it contained much below 32°, and 
consequently when the water spray was added the water 
was only partially frozen. 
I subsequently improved the apparatus so as to be able to 
regulate the supply of water and ether to the condition of 
the air. 
The Apparatus. 
This is shown in the accompanying sketch. It consists 
of a brass tube half an inch in diameter, one end of which 
is connected with bellows capable of maintaining a constant 
pressure of about 18 inches of water, on the other end of 
the tube is a cap over the end of which is a flat plate or 
diaphragm having a central opening of an inch in 
diameter which forms the aperture for the blast. Entering 
through the sides of the main brass tube are two small 
brass tubes which reach to within J an inch of the plate and 
into the ends of which are sealed fine glass capillary tubes’ 
the glass being very thin; these protrude just through 
the middle of the aperture* the one about r 6 - of an inch 
and the other -h. Through these tubes the water and 
ether are separately introduced into the blast to form the 
spray, and it is mainly on the adjustment of these tubes that 
the efficiency of the apparatus depends. It is essential that 
