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heat the pores are opened, and these metals admit of, encourage 
indeed, the diffusion of gases. “ Such a species of porosity,” 
says Graham, a if it exists, may well be expected to throw a 
light on the distance of solid molecules at elevated tempera- 
tures when gases introduce themselves. The experiments were 
essentially of the following character. A vacuum was produced 
in a platinum tube placed within a porcelain tube charged with 
hydrogen ; this tube was raised to a red heat, and the dense 
metal then became permeable to hydrogen. The same result 
was obtained with iron. 
The passage of a gas through a colloid septum is preceded 
by a condensation of the gas in the substance of the septum. 
“ Is,” asks Mr. Graham, u a plate of ignited platinum capable, 
then, of condensing and liquefying hydrogen gas?” By an 
ingenious arrangement the experiment was made, and the 
result proved that platinum exhibited a new property — the 
power to absorb hydrogen at a red heat , and to retain that 
gas at a temperature under redness for an indefinite time. It 
may be allowable to speak of this phenomenon as a power to 
occlude (to shut up) hydrogen, and of the result as the 
occlusion of hydrogen by platinum. Experiments were made 
with many other metals, and their powers of occlusion carefully 
determined ; that of iron alone can be mentioned in this paper. 
This was determined by first exhausting iron of any gases held 
within its pores by exposing it to a high temperature, and then 
cooling it gradually in hydrogen gas ; the metal absorbed and 
retained this gas after cooling. The iron experimented on was 
capable of holding 0*46 volume of hydrogen ; but when the 
same specimen of iron was charged with carbonic oxide gas in 
the same manner, it was found to be capable of taking up at a 
low red heat and holding when cold 4T5 volumes of carbonic 
oxide gas. This discovery cannot fail to have a bearing on the 
important process of steel manufacture. 
Pursuing this extraordinary line of enquiry, and obtaining at 
every step new, confirmatory, and beautiful results, it was re- 
solved to ascertain if the masses of matter obtained from the 
atmosphere — Meteoric Stones — and which bear evidence of 
having been at a very high temperature, gave any indication 
of the kind of atmosphere in which they were formed. 
A slice from the meteoric iron of Lenarto, which was analysed 
by Wehrle, and found to be of sp. gr. 7*79, and to consist of iron 
90*883, nickel 8*450, cobalt 0*665, and copper 0*002, was 
obtained. This was made the subject of careful experiment, 
and the Lenarto iron yielded 2*85 times its volume of gas, of 
which 86 per cent, nearly was hydrogen. 
“ Hydrogen has been recognised,” says Mr. Graham, “ in the 
spectrum analysis of the fixed stars, by Messrs. Huggins and 
