112 Report on the Miscellaneotis Implements 
procured, while, in the small quantities used in these machines, 
quite harmless to life or health should any escape occur. 
The machine consists of the following parts : — 
1. A " refrigeratoi-," where the carbonic anhydride passes by expansion 
into the gaseous state, causing, by such expansion, intense cold. 
2. A compressing pump, wherein the expanded gas is re-compressed; and 
3. A condenser, where tlie compressed gas is liquefied by cooling water. 
Besides the gas pump, there are two auxiliai-y pumps, one supplying the 
cooling water to the condenser, the other circulating brine in the pipes on 
the roof of the cold chamber. All three pumps are driven from the same 
cross-head, and direct from the steam cylinder. 
The parts described above are analogous to those used in 
ammonia, ether, and sulphurous-acid machines, which all work 
on the principle of compression, liquefaction, and evaporation of 
gases, but, owing to the larger range of expansion and intense 
cold produced hj carbonic anhydride, the quantity required both 
of this and cooling water, together with the size of the machine, 
is much reduced. 
The joressure required to liquefy carbonic anhydride is high, 
but does not exceed that used in ordinary hydraulic machinery, 
while the compressing pump, pipes, &c., are of such small dimen- 
sions that no difficulty is met with in insuring abundance of 
strength and substantial tightness. In addition, the quantity 
of carbonic anhydride required to charge the machine is so small 
that no danger to life or health would arise even if, by some 
accident, the entire quantity in the machine were thrown sud- 
denly into the engine-room. 
The cycle of operation is as follows : — 
The machine is charged with CO,, condensed into liquid form under a 
pressure of 50 atmospheres, at a temperature of 58° Fahr. It is at present 
the custom of the makers to buy this liquid from Germany, at a cost of 6d. 
per pound. 
Escaping from the bottle in which it is confined, the liquid CO^ expands 
into a chamber (consisting of a coil of pipe), where it resumes its gaseous 
form, and is afterwards pumped into the condenser. The act of compression 
heats the expanded gas, and tlie heat so formed is carried away by water 
flov.-ing through a jacket surrounding the condenser. 
The compressed gas passes next through a regulating valve in a very 
fine stream into the refrigerator, which consists of a coil surrounded by brine. 
The expansion of the gas in the refrigerator cools the surrounding brine 
down to 20° or 25° Fahr., and the cold brine then circulates through pipes 
arranged in the usual way upon the ceiling of the cooling chamber. 
These engines are made from 1 to 70 horse-power, with a 
capacity for ice production wdiich varies from ^ cwt. to 2 tons 
per hour. 
The Elastic Steel Horse-Collar Company^ of 72 Summer Row, 
I^irmingham, exhibited a steel horse collar (Art. 4594) which con- 
