98 
Proceedings of the Royal Society of Edinburgh. [Sess. 
guidance of Government research officers they are being successfully 
produced in this country. 
The most convenient size of liquid air or liquid oxygen container, or 
storage and transport flask, is designed to carry 50 lbs. of the fluid. 
A metal container of this capacity and of proportions usual at the present 
time is shown in sectional elevation in fig. 1. It consists of inner and 
outer spheres, A and B, respectively 14 and 15 ins. in diameter, the inner 
one being suspended by a thin, narrow 
neck, C, of low-conductivity alloy which 
is soldered at its upper end into a metal 
plug, E. The space between the globes 
is evacuated through a lead pipe, G, 
which, when the operation is complete, 
is squeezed flat and sealed off by means 
of a flame ; the pipe is finally protected 
(as is shown) by a metal cap containing 
bitumen or wax in which the end of the 
tube is embedded. The care needed 
in making these bottles will to some 
extent be realised from the fact that a 
high vacuum requires to be maintained 
through the agency of seven soldered 
joints. A dish-shaped metal spinning, 
F, is attached to the lower half of 
the inner globe, and holds activated 
charcoal. This important addition is 
due to Dewar ; without it, even a well- 
made and well-evacuated metal flask 
would not long hold a high vacuum. 
In the container illustrated, the charcoal 
is connected to the vacuum space by means of one or more openings 
in the dish, the openings being covered by fine gauze. At liquid-air 
temperature the charcoals power of adsorption is very strong; it draws 
into and retains in its own capillaries and inter-molecular passages most of 
the residual gas in the vacuum space, and therefore automatically preserves 
the high degree of vacuum needed. 
The inner surface of the outer globe and the outer surfaces of the inner 
globe and charcoal dish are highly polished, to reduce as far as possible the 
heat transferred across the vacuum space by radiation. 
Most of the containers made in this country are constructed of copper — 
