SEPTEMBER II, 1913] 
NAIURE 
29 
organisms as is desirable for the domestic science 
student. It is divided into five sections, dealing 
respectively with (a) morphology and classifica- 
tion; (b) cultivation and methods of investigation ; 
{c) physiology; (d) fermentation; and (e) micro- 
organisms in relation to health and disease. The 
bacteria, yeasts, and moulds are considered at 
some length, and a chapter on parasitic Protozoa 
is included. . 
The chapters on general morphology and classi- 
fication are particularly good, and a clear account 
is furnished of the distinguishing features of the 
various groups. In an appendix an illustrated key 
is given of the families and genera of the common 
moulds; this will be found most useful in the 
laboratory by other than domestic science students. 
The brief description of the optics of the im- 
mersion system of lenses is correct, so far as it 
goes, but a paragraph should have been inserted 
pointing out that the great advantage of this 
system is the increased resoluion obtained thereby. 
The chapter on food preservation is a useful 
summary of the subject, but might have been 
extended with advantage. 
The chapters on the nitrogen cycle in nature, 
alcoholic and other fermentations, enzyme action, 
and the ripening of certain foods are all satisfac- 
tory and convey a considerable amount of coordin- 
ated information on these important aspects of 
microbiology. 
Much space (140 pages) is devoted to a con- 
sideration of disease and disease-producing micro- 
organisms, vegetable and protozoal. We think 
this section could have been somewhat curtailed 
with advantage, having regard to the avowed 
limitation of the book; and the space so gained 
might then have been devoted to a fuller con- 
sideration of certain aspects of household micro- 
biology. Such criticisms as have been offered are 
those of detail, but the book as a whole is an 
excellent one. It is profusely and well illustrated, 
and can be strongly recommended not only to the 
domestic science student, but to a wider public. 
R. T. Hew err. 
Aus Siid-Brasilien. Erinnerungen und Auf- 
seichnungen. By Dr. W. Breitenbach. Pp. 
XVi+-251. (Brackwede i. W.: Dr. W. Breiten- 
bach, 1913.) Price 3 marks. 
THE author has lived in southern Brazil for 
several years in order to observe the land and the 
people, especially the German colonies, and be- 
ginning in the year 1884, he has since described 
his observations in more than thirty newspaper 
articles, essays, and separate pamphlets. Con- 
sidering the changes which have come about in 
Brazil within the last thirty years, this book does 
not pretend to deal with present-day questions of 
commerce, industry, and general development, 
or with the colonisation scheme, which, of course, 
has undergone complete modifications. His per- 
sonal experiences, narratives of various journeys, 
are also omitted, having been described elsewhere. 
It is, therefore, not very obvious why these 
“reminiscences and notes” should be published 
now. 
NO. 2289, VOL. 92] 
The fragmentary chapters on minerals, fauna, 
and flora are poor. Others, written in the easy, 
fluent style of feuilletons or causeries, deal with the 
life in towns, chiefly Porto Alegre, the capital of 
South Brazilian Germans, whose customs, modes 
of assimilation, ideals, and successes are compared 
with those of the Brazilians. 
LETTERS TO THE EDITOR. 
[Tke Editor does not hold himseif responsible for 
opinions expressed by his correspondents. Neither 
can he undertake to return, or to correspond with 
the writers of, rejected manuscripts intended for 
this or any other part of Nature. No notice is 
taken of anonymous communications.] 
Branch Product in Actinium C. 
Ir is now well established that the atoms of 
radium C and thorium C can break up in two distinct 
ways, 7.e., with the expulsion of either an a or a B 
particle. It is to be expected from the close analogy 
between the C products of the various radio-active 
families that actinium C should also show abnormal 
disintegration, and, further, it might be anticipated 
that one of the branch products would emit an « 
particle with great velocity and corresponding long 
range. We have made experiments to test this point. 
A source of actinium active deposit was covered with 
a sheet of mica equivalent to about 5 cm. air in 
stopping power of a particles, and the whole placed 
in an exhausted chamber with a zinc sulphide screen 
about 2 cm. from the source. The numbers of 
scintillations appearing on the screen per minute 
for different pressures of the air inside the 
apparatus were counted, and thus the falling off of 
the a particles with ‘“range’’ determined. The 
results showed that in addition to the « particles of 
actinium C with range 5.4 cm., a small number, 
about 1 in 600, can penetrate as far as about 6-45 cm. 
Special experiments showed that the long-range a 
particles could not be due to radium or thorium 
impurity, and they must therefore be attributed to 
the expected new branch product. 
In connection with this question, it should be 
noticed that Mme. Blanquies, in 1910, inferred the 
existence of two a-ray products in the active deposit 
of actinium from the shape of the Bragg ionisation 
curve. The small fraction of long-range « particles 
found in our experiments, viz., 1 in 600, is, however, 
quite insufficient to be reconciled with her results. 
We are therefore repeating her experiments. 
E. Marspen. 
R. H. Witson. 
University of Manchester, September 3. 
The Terrestrial Distribution of the Radio-elements 
and the Origin of the Earth. 
In Nature of June 19 and August 7, 1913, Mr. 
Holmes, in two interesting letters, shows on the basis 
of the planetesimal hypothesis how a concentration 
of the radio-elements might possibly take place in the 
earth’s crust with their absence at depth to satis- 
factorily account for the observed temperature gradient 
of the earth; and in his latest communication he 
indicates how the inhibition of radio-activity by pres- 
sure might bring about the same result. But the 
terrestrial distribution of these elements seems to be 
of further importance in that it may enable us to 
determine whether our earth had a stellar or a 
planetesimal origin. 
On the stellar hypothesis, the earth would be partly 
developed by a process of oxidation—practically the 
i same as that by which we manufacture steel from 
