350 
its Connection with Rock-Formation.’ Experi- 
ments were carried out to determine whether 
under the influence of great pressure solid par- 
ticles, which do not under ordinary circumstances 
unite, might be made to cohere. The pressure 
used in the experiments was about 10,000 at- 
mospheres, and this pressure could be exerted 
if necessary at a temperature as high as 400°. 
All bodies which are plastic under pressure 
were found to cohere as if they had been fused, 
while those substances which are not malleable 
remained in a powder after exposure to the 
greatest pressures. Thus sand, calcium car- 
bonate, alumina and oxid of iron did not 
cohere, and since the pressure used corresponds 
to a column of sand fifty kilometers in height, 
pressure alone can not be the cause of the for- 
mation of rocks from these materials. Metallic 
powders, on the other hand, cohere perfectly, 
which must be due to a kind of solid solution. 
That this is probable is shown by using mix- 
tures of different metals, in which case alloys 
are formed as perfectly as by fusion. Those 
metals, however, which do not alloy by fusion, 
as lead and zinc, will not alloy under pressure. 
That these alloys were not occasioned by a 
mere mixing under pressure was shown by 
placing together without pressure cylinders of 
the same and of different metals. Even in the 
cold there was some adherence and, when 
heated to a temperature far below the point of 
fusion, a perfect union was obtained in a few 
hours. In the case of the union of different 
metals, an alloy was formed at the line of junc- 
tion, which with tin and lead was six millimeters 
in thickness. Compounds were readily formed 
by pressure in those instances where the vol- 
ume of the compound is less than that of its 
constituent elements, as with silver and sul- 
phur ; on the other hand, compounds which oc- 
cupy more space than their constituents were 
dissociated by pressure. Thus copper calcium 
acetate was decomposed into copper acetate, 
calcium acetate and water. In those cases 
where solution is accompanied by contraction, 
the presence of water was found to greatly as- 
sist in the formation of solid masses from the 
powders, and solid carbonates were readily 
formed. A solution of silicic acid alone did not 
cause agglutination of sand, owing to the great 
SCIENCE. 
[N. S. Vou. XIII. No. 322: 
contraction on drying, but when combined with 
even low pressure, solidification to a consider- 
able extent was obtained. All these influences 
have played a part in rock formation. 
ARSENIC IN COPPER. 
LITTLE is given in chemical literature regard- 
ing the effect of small quantities of arsenic upon 
copper, a subject of much importance at the 
present day. A series of experiments is de- 
scribed by Ernest A. Lewis in the Chemical 
News, in which arsenic was added to a copper 
99.843 per cent. pure, and the resultant metal 
studied photomicrographically and as to its 
physical properties. Malleability is not appre- 
ciably affected by small quantities of arsenic (up 
to 1.8 per cent.), the samples with 1 per cent. 
and with 1.37 per cent. rolling particularly well. 
The tensile strength is from 3 to 5 tons higher 
than that of ordinary sheet copper, the limit of 
elasticity is about 3 tons per square inch higher, 
and the elongation isnot reduced. From micro- 
graphical examination, the metal appears to 
consist of crystals of copper, in a eutectic of 
copper arsenid or a solution of copper arsenid 
in copper. In copper intended for rolling, ex- 
cept that for electrical purposes, the presence 
of asmall amount of arsenic appears to be a dis- 
tinct advantage, but nothing is gained by hav- 
ing more than 0.5 per cent. present. 
ATMOSPHERIC HYDROGEN. 
AN interesting result of Professor Dewar’s 
latest experiments, in conjunction with Profes- 
sor Liveing, on the more volatile of the inert 
gases of the atmosphere is the demonstration 
that hydrogen exists free in the atmosphere in 
sensible proportion. There has been much 
question in the past as to its presence, which 
has not been heretofore satisfactorily proved ; 
indeed the velocity of the hydrogen molecule 
renders it doubtful as to whether hydrogen 
would not escape from the earth into inter- 
planetary space. On this basis there must be a 
continual accession of hydrogen to this planet 
from the interplanetary space, and hence possi- 
bly of the elements which occasion the lines of 
the nebular and coronal spectra. Some indica- 
tions in this direction have been found in the 
atmospheric inert gases, and these are now 
being studied from this standpoint. J. L. H. 
