AUGUST 13, 1914 | 
there is the experimental evidence; both strain- 
hardened metal and quenched steel on etching exhibit 
the well-defined oriented lustre of a crystalline aggre- 
gate, thus clearly showing that the crystals are not 
disarranged into minute irregular fragments. It 
would seem, therefore, that Mr. McCance’s conclu- 
sions must be narrowed down to this, that the hard- 
ness of quenched steel is due to the same cause as 
the hardness of strain-hardened iron, and this—but 
for a difference as to mode of origin—is also the view 
of Edwards and Carpenter. In this narrowed con- 
clusion, however, there is a distinct step forward, since 
we have a definite ‘‘explanation "of the hardening 
of steel in the sense that this phenomenon is cor- 
related with the much larger class of phenomena 
which occur when any soft or ductile metal is hardened 
by plastic strain. If we accept the possible existence 
of the amorphous phase, it is easy to express both 
classes of facts in a single and simple formula, and 
this in itself constitutes another argument in support 
of the amorphous theory. Whatever view one may 
take of these admittedly hypothetical matters, it seems 
that a definite advance has at last been made in our 
knowledge of the hardening of metals. 
W. ROSENHAIN. 
SCHOOLS AND EMPLOYERS IN THE 
UNITED STATES:+ 
ISS WINEFRID JEVONS gives in the report 
before us an interesting account of the history and 
present position of the relations between the schools 
and industrial employment in the United States. 
The most important lesson to be learnt from the 
report is, perhaps, that in the United States employers 
and trade unions have realised, to a much greater 
extent than in this country, the necessity for part-time 
day classes for persons engaged in industry and com- 
merce. Not only does the American Confederation of 
Labour take this view, but the National Association of 
Manufacturers also favours it. Indeed, the latter body 
went so far in 19:2 as to recommend compulsory 
continuation classes, until the seventeenth or 
eighteenth year, one half-day a week, without loss of 
wages. 
In this country there are some firms (comparatively 
few in number) who have had the wisdom to see that 
it is not only in the interest of the people they 
employ but also in their own interest to liberate 
young persons a certain number of hours a week, in 
order that they may in the daytime receive proper 
part-time instruction directed to make them more 
efficient in their respective industries; but we are still 
far from so wide and generous a belief in the value 
of education as the resolutions of the National Asso- 
ciation of Manufacturers show to be prevalent in the 
United States. 
The existence of such a wholesome state of public 
opinion accounts for the large amount of voluntary 
and compulsory part-time instruction which is to be 
found throughout the States; many instances of this 
are given in the report. In Massachusetts, a law has 
been enacted which enables local authorities to open 
day continuation classes for the education of children 
between fourteen and sixteen who are in regular 
employment, and to compel attendance at these classes 
in the daytime for not fewer than four hours a week; 
the time spent in the school is counted as a part of 
the number of hours that the child is permitted by 
law to work. The State provides half of the cost of 
the maintenance of the classes. 
In the States of Ohio and Wisconsin, compulsory 
1 Board of Education. 
B Special Reports on Educational Subjects, vol. 
XXVI111. 
NO. 2337, VOL. 93] 
NATURE 
627 
day continuation classes are in existence; in the latter 
State, apprentices may not be employed for more than 
55 hours a week, and the employer must liberate the 
apprentice five of these 55 hours a week in order that 
he may attend a day continuation school. 
J. We 
SEISMOMETRY AND ENGINEERING.! 
N the memoir before us we have a gratifying proof 
that practical engineers realise the importance of 
the application of the principles of instrumental seis- 
mometry to building construction. The immediate 
object in the present investigation is the vibration set 
up in a large masonry bounding wall of a reservoir in 
Queistal, Schleswig. This wall stretches between 
rocks across a narrow valley, and the overflow of 
water, estimated at 100 cubic metres a second, falls 
about 4o metres. Thus an enormous amount of vibra- 
tional energy is set up. 
The destructive action of vibration on a structure 
is probably determined by the maximum acceleration 
experienced, and thus short-period vibrations are often 
more serious than long-period vibrations of larger 
amplitude. Prof. Grunma h first describes and dis- 
cusses an apparatus designed to give the maximum 
acceleration, and then goes on to describe the arrange- 
ments for investigating the period and amplitude. 
These are really seismographs for measuring the hori- 
zontal and vertical components of motion. They are 
based on precisely the principle of electromagnetic 
registration introduced by Prince Galitzin for earth- 
quake recording. The apparatus differs from Galit- 
zin’s in detail considerably, since the periods and 
amplitudes to be measured are very different from 
those experienced by the passage of earthquake waves. 
Continuous registration was made, and excellent dia- 
grams of the results are given. It appears that the 
periods ranged from about 0-03 sec. to 0-003 sec., 
and the amplitude from o-oo1 mm. to 0-00005 mm. 
The theoretical discussion of electromagnetic regis- 
tration given appears somewhat inadequate. The 
author adopts what may be called an equilibrium 
theory instead of a dynamical one. It is possible that 
this may be accurate enough in the case considered, 
but one would like a demonstration that this is so. 
The memoir will no doubt be appreciated by 
engineers and seismologists alike. G. W. W. 
RECENT BOTANICAL WORK IN 
DENMARK. 
yANes the general meeting of the Danish Botanical 
Society in 1g12 it was decided to publish in the 
future two distinct journals. One of these is the 
Botanisk Tidsskrift, the society’s old periodical, which 
has reached its thirty-third volume, and contains 
chiefly papers on the Danish flora, besides articles 
on subjects of more general botanical interest. This 
will continue on its former lines, being written mostly 
in Danish, though occasionally—much too rarely, it 
may be said, for non-Danish readers—with abstracts 
in English, French, or German. The second journal 
is a new venture, the Dansk Botanisk Arkiv, pub- 
lished at indefinite periods, and containing mono- 
graphs and other special articles in either of the four 
languages mentioned. Both journals are sent post 
free to members of the society, membership being open 
to all on payment of to Kronen (11Is.) a year; the 
subscription for the Botanisk Tidsskrift alone is 
6 kronen, and the numbers of the Arkiv may be pur- 
1 ‘* Experimentaluntersuchung zur Messung von Erderschiitterungen. 
By Prof. L. Grunmach. Pp. 102. (Ber.in: Leonhard Simion Nf., 1913. 
