1878.] Liquefaction of Oxygen . 243 
length as the envelope. These two tubes are closed by a 
common base. 
In the central tube is retained compressed carbonic acid 
produced by the reaction of hydrochloric acid on Carrara 
marble. This gas, being dried, is stored in an oil gasometer 
(g) of 1 cubic metre capacity. 
At a pressure of from 4 to 6 atmospheres the carbonic acid 
easily liquefies under these circumstances. The resulting 
liquid is led into a long copper tube (b), 4 metres in length 
and 4 centimetres in diameter. 
Two pumps, p x and p 2 , coupled together like the first, ex- 
haust carbonic acid either from the gasometer (g) or from 
the long tube (b) full of liquid carbonic acid. 
The ingress to these pumps is governed by a three-way 
tap, H. A screw valve cuts off at will the ingress of liquid 
carbonic acid in the long tube ; it is situated between the 
condenser of carbonic acid and this long tube. When this 
screw valve is closed, and the two pumps draw the vapour 
from the liquid carbonic acid contained in the tube 4 metres 
long, the greatest possible lowering of temperature is pro- 
duced ; the carbonic acid solidifies and descends to about 
— 140°. The subtraction of heat is maintained by the 
working of the pumps, the cylinders -of which take out 
3 litres per stroke, and the speed is 100 revolutions a 
minute. 
Both the sulphurous acid tube and the carbonic acid tube 
are covered with a casing of wood and non-conducting stuff 
to intercept radiation. 
In the interior of the carbonic acid tube, B, passes a fourth 
tube, A, intended for the compression of oxygen ; it is 5 metres 
long and 14 millimetres in external diameter. Its internal 
diameter is 4 millimetres. This long tube is consequently 
immersed in solid carbonic acid, and its whole surface is 
brought to the lowest obtainable temperature. These two 
long tubes are connected by the ends of the carbonic acid 
tube, consequently the small tube extends about 1 metre 
beyond the other. I have curved this portion downwards, 
and given the two long tubes a slightly inclined position, but 
still very near the horizontal, as I have shown in the accom- 
panying drawing. 
The small central tube is curved at A, and screws into the 
neck of a large howitzer shell, c, the sides of which are 
35 millimetres thick ; the height is 28 centimetres, and the 
diameter 17 centimetres. 
This shell contains 700 grins, of chlorate of potash and 
256 grms. of chloride of potassium mixed together, fused, 
R2 
