FEBRUARY 19, 1914] 
NATURE 
697 
Some of the scientific and technical periodicals of 
Germany are beginning to use the symbols agreed on 
by the International Committee on units and symbols, 
and it may be useful to mention here some of the 
symbols adopted. Length J, mass m, time t, radius, r, 
volume V, velocity v, gravitational acceleration g, 
pressure p, temperature absolute T or 6, ordinary t, 
quantity of heat Q, specific heat at constant pressure 
Cp, at constant volume c,, coefficient of linear expan- 
sion a, wave-length \, intensity of magnetisation, 3, 
magnetic field 5, magnetic induction B, permeability 
susceptibility x, electric current I, resistance R, electro- 
motive force E, capacity C, quantity of electricity Q, 
self-inductance L. 
Tue Institution of Electrical Engineers has issued a 
programme of the meetings to be held by its local 
sections until the end of May next. The seven sec- 
tions are :—Birmingham, holding its meetings at the 
University there; Dublin, holding its meetings at the 
Royal College of Science; Manchester, meeting at the 
physical laboratory of the University; Newcastle, 
which, in addition to the meetings at the Armstrong 
College of Science, has arranged also three meetings | 
at Middlesbrough; the Scottish, with meetings at 
Edinburgh and Glasgow; the Western, with meetings 
at Bristol and Cardiff; and the Yorkshire Local Sec- 
tion, meeting at the Philosophical Hall, Leeds, 
In connection with wave-length and other measure- 
ments in wireless telegraphy, adjustable condensers 
are frequently employed, and in many cases the quan- 
tity to be measured varies with the square of the 
capacity of the condenser. Fot such purposes, there- 
fore, an adjustable condenser following a square law 
should be useful, and Mr. W. Duddell, in a short - 
paper in the Journal of the Institution of Electrical 
Engineers for February 2, describes the method he 
has used for working out the correct curve to give 
to the plates of a rotating sector condenser, with this 
object in view. The data obtained may save other 
experimenters from going through the work a second 
time. 
Tue British Fire Prevention Committee have found 
it necessary to formulate a standard test and a model 
specification for portable chemical fire extinguishers 
owing to the fact that several fatalities have occurred 
through these appliances bursting when being 
operated. There is at the present moment an unfor- 
tunate tendency to put various types of ‘‘cheap-jack”’ 
appliances on the market, and the committee direct 
attention to the reprehensible method which is fre- 
quently adopted by makers or their agents in country 
towns and villages of making use of faked demon- 
stration tests to sell such appliances. The specifica- 
tion can be obtained from the offices of the committee, 
8 Waterloo Place, Pall Mall, S.W. 
No. 13 of the Technologic Papers of the Bureau of 
Standards of the Department of Commerce of the 
United States deals with the question of electrolysis 
in concrete, and is an experimental investigation of 
the problem by Messrs. E. B. Rosa, Burton McCollum, 
and O. S. Peters. The report is illustrated by 
numerous photographs and tables of data, and fills 
NO. 2312, VOL. 92] 
136 pages. Of the numerous theories that have been 
advanced to account for the cracking of reinforced con- 
crete that one which attributes it to the oxidation of 
the iron anode following electrolytic corrosion has been 
fully established. The oxides formed occupy a volume 
which is 2-2 times as great as the original iron, and 
the pressure resulting from this causes the block to 
crack open. Many points of great interest to the 
architect and engineer are dealt with in full detail in 
the report. 
HitHErtTO aéroplane problems have received very 
little attention from workers in pure science, and it is 
not so very fong ago that an attempt by Prof, Herbert 
Chatley to investigate mathematically the stresses in 
the various parts of an aéroplane met with a very 
discouraging reception. We have now received a 
paper by Prof. H. Reissner on the strength of flying 
machines, published in the Jahrbuch der wissen- 
schaftlichen Gesellschaft fiir Flugtechnik, vol. i., 
dealing with the general principles involved in the 
study of aéroplane stresses. As the author points 
out, the increasing use of aéroplanes in all kinds of 
weather, often driven at high speeds for racing pur- 
poses carrying heavier loads, and subjected to vibra- 
tion for extended periods, has brought this question 
of safety into greatly increased prominence. Among 
various methods of testing strength, one consists in 
suspending the machine in an inverted position and 
loading its supporting surfaces with sand. Prof. 
Reissner advocates experiments in which aéroplanes 
are strained to the breaking point, although the cost 
of such tests would preclude them from being made 
except when a large number of machines of a particu- 
lar type are being built. At the present time all 
aéroplanes have some of their parts strained beyond 
the elastic limits of the materials, a circumstance 
which greatly increases the difficulty of the problem. 
Mr. Sit Asput-Art dealt with the doctrine of the 
first matter as held by the alchemists, and particularly 
by Thomas Vaughan, in a paper read before the 
Alchemical Society on February 13. He pointed out 
that the alchemical quest was of a different nature 
from that pursued by the experimental chemist, and 
needed a different mental point of view for its appre- 
ciation. Alchemy, he said, had a secret tradition, 
and, in that light, a scriptural faith; it started with a 
theory of creation and a psychic doctrine, a symbolic 
presentation of which it sought in a chemical experi- 
ment. The lecture was mainly concerned with the 
doctrinal implications of this “ first matter,” and their 
significance for modern philosophy. 
THE sixteenth technological paper from the Bureau 
of Standards (Washington) deals with the manufac- 
ture of lime. It describes an attempt to study the 
effects of various impurities on the properties of lime, 
and to compare the efficiency of various types of 
manufacturing processes used in the transformation of 
limestone into slaked- and quick-lime. The brochure 
is a particularly interesting contribution to the litera- 
ture of that neglected industry—lime burning; the 
pamphlet is of equal interest to the consumers—archi- 
tects and builders—since they seek the best possible 
mortar, &c., for building purposes. The quality of 
