FEBRUARY 19, 1914] 
_ beam was examined on a photographic plate. It was 
found that the untreated specimen gave no definite 
reflection. In the case of the annealed specimen, how- 
ever, spots were observed on the plate indicating that 
there were now present in the metal, crystals big 
enough to reflect quite an appreciable portion of the 
beam in definite directions. The same results were 
observed whether the surfaces were highly polished 
or badly tarnished. 
On passing beams of X-rays through various metallic 
crystals, e.g. antimony, zinc, aluminium alloy (50 per 
cent. Al and 50 per cent. Cu), Laue spots were 
observed on The spots 
the photographic plates. 
obtained on transmission through an antimony crystal 
are shown in the adjoining photograph. Owing, 
however, to the difficulty of procuring individual 
crystals of the metals, symmetrical Laue patterns 
have not yet been obtained. The experiments, how- 
ever, show that this method of investigating meétallic 
crystals may prove very helpful to the metallurgist. 
A. Owen. 
G. G. Brake. 
Teddington, February 9. 
The Magneteon and Planck’s Constant. 
Tue relation between the magneton and Planck’s 
constant is even more intimate than Dr. Allen’s re- 
marks (Nature February 5), and his numerical illus- 
tration would suggest. 
Using the notation employed by Dr. Allen, an 
electron (charge e, mass m) moving in a circular orbit 
{radius a) with angular velocity w» would have angular 
momentum ma*w, and magnetic moment 3ea7o. On 
Dr. Bohr’s hypothesis the angular momentum is 
related to Planck’s constant h by the relation 
ma*w=h/2x7, and the magnetic moment becomes e/m 
h/4az, as Dr. Allen indicates. 
The value of the magnetic moment per atom gram 
ei UG 
is n— — —, 
m qn k 
per atom, and R and k the constants of the gas 
theory, so that R/k is the ratio of the atom gram to 
the atom. 
where n is the number of such electrons 
Y e of 
Taking — =1°772 49 
bs 772 10 
“= 1437 (from radiation measurements) 
R=8°316 35’, 
we have the magnetic moment per atom gram 
=n 5617-1. But the magnetic moment per atom 
Non 2302, VOL. 92] 
NATURE 
687 
gram, as given by Weiss (‘‘Idées Modernes sur la 
Constitution de la Matiére,” p. 334), is 1123:5, so that 
the number of such electrons in five atoms is equal 
to the number of magnetons per atom, as defined by 
Weiss, with the accuracy of Weiss’s measurements 
and that of the constants above. 
If instead of Bohr’s hypothesis, the alternate one, 
that the angular momentum is equal to h/z, be em- 
ployed, the five is replaced by ten. This seems to 
indicate that, in the magnetic materials, there is a 
unit of five (or ten) atoms, which has a constant 
number of magnetons. 
The above results were stated by the writer in the 
discussion on radiation at the British Association, 
Birmingham, 1913. S. D. CHALMERS. 
The Northampton Institute, Clerkenwell, E.C., 
February 7. 
Zonal Structure in Colloids. 
Ir Mr. George Abbott (Naturr, January 29, p. 607) 
will refer to the paper by Prof. J. W. Gregory and 
myself on eozoonal structure in the ejected blocks of 
metamorphosed limestones of Monte Somma and Vesu- 
vius he will find that twenty years ago I explained 
the mechanism of zonal structure, and showed it to 
be of osmotic origin in that and other cases. This 
has been amply confirmed by further investigation 
into illustrations of my ‘‘osmotic theory” of meta- 
morphism, and, although paid little attention to by my 
own countrymen, is amply credited by the recent pub- 
lications of Liesegang and Kurd Endell. 
Amongst several of my papers will be found refer- 
ences to concentric laminated structure in such objects 
as spherulites, oolites, pisolites, calculi, &c. This I 
would attribute to zones of chemical exhaustion or 
surplus, which, in the end, is very nearly related to 
chemical exhaustion or surplus in osmotic interchange. 
H. J. Jonnston-Lavis. 
Beaulieu-sur-Mer (A.M.), France, 
February 1. 
Dr. Jounston-Lavis’s letter is indeed welcome; 
it confirms my own impression that English geologists 
have neglected concretionary processes. During my 
fifteen years of observation of the Fulwell beds no one 
ever suggested osmosis to me before Prof. S. Leduc. 
Even the authorities of the British Museum, South 
Kensington, whilst accepting a large number of my 
best specimens—some of them I cannot replace—have 
since repeatedly refused to give them the benefit of a 
modern classification, because none could be ‘“ recog- 
nised.”’ 
Few persons realise the great ‘“‘ experiment ’’ made by 
nature at Sunderland, where there are two square 
miles of limestone, 130 ft. thick, associated with 
70 ft. of the so-called marl beds. All the limestone 
shows magnificently the unique concretionary structure 
such as is unknown elsewhere in England, and, pos- 
sibly, in the world. 
The osmotic influence, or ‘‘osmotic interchange,” 
as Prof. Johnson-Lavis calls it (Prof. Kiister, of Bonn, 
in a recent letter to me says, “rhythmical precipita- 
tion, not osmosis’’) has operated in, and through, 
all the 130 ft. of rock, whilst the forces of crystallisa- 
tion must have been subsequent and partial. 
The change apparently took place after the strata 
had become solid enough for the formation of ordinary 
joints, the structure being conspicuous in starting 
from joints and bedding planes, whilst the pattern 
is very seldom seen to cross them.  Pisolites and 
spherulites are, of course, common. 
GEORGE ABBOTT. 
Rusthall Park, Tunbridge Wells, February 9. 
