<b ohaell 
DeEcEMBER 18, 1913] ‘ 
with the two new professors. At present there are 
117 students working specially at chemistry, includ- 
ing its technological applications, of which number 
thirty-six are engaged in research. In addition, the 
department provides the subsidiary training in chem- 
istry for about 329 other students. 
THE annual prize distribution of the Sir John Cass 
Technical Institute was held on Wednesday, Decem- 
ber 10, when the prizes were distributed by Sir 
Thomas H. Elliott, K.C.B., Deputy Master and 
Comptroller of the Royal Mint. The chair was taken 
by Sir Owen Roberts, chairman of the governing 
body of the institute. Sir Thomas Elliott, in address- 
ing the students, spoke of the desirability of keeping 
in view the aim of the instruction provided at the 
institute, the object of its work, and the extent to 
which this object was being accomplished. He was 
himself disposed to say that the primary purpose for 
which the institute exists is to assist students to do 
justice to themselves and to those who may be or 
become dependent upon them, to enable them to per- 
form services which the community requires and for 
which the community is prepared to pay, and to pay 
well, to increase their earning powers, and so to help 
them to secure a better livelihood for themselves than 
would otherwise be theirs. He counselled the students 
not to be afraid of selecting a manual occupation and 
in connection with it to endeavour to learn all the 
facts connected with the material used, the machinery 
employed, and the scientific principles upon which 
the work is based. The Rey. J. F. Marr, chairman 
of the institute committee, gave a summary account 
of the work of the institute during the past session, 
in which he referred especially to the increasing num- 
ber of students, the research work that had been 
carried on in the institute, both by students and by 
members of the staff, and the several developments 
in the courses of instruction provided. In the latter 
connection details were given of the work on col- 
loids, on the theory and applications of mathematical 
statistics, on the fermentation industries, on mine 
sampling and valuing, on metals used in the motor- 
car industry, and on the casting of metals, all sub- 
jects which had received the special attention of the 
governing body during the past session. 
SOCIETIES AND ACADEMIES. 
Lonpon. 
Physical Society, November 28.—Prof. C. H. Lees, 
F.R.S., vice-president, in the chair.—Prof. H. L. 
Callendar; The expansion of silica. In attempt- 
ing to deduce the expansion of mercury by 
the weight thermometer method with silica bulbs 
it was necessary to determine the expansion 
of specimens of silica from the same source as 
the bulbs, and to extend the observations of expansion 
over the range o° C. to 300° C. Specimens which 
had been exposed to high temperatures appeared to 
give lower results over the range 0° C. to 300° C. 
than specimens which had not been heated above 
300° C. during the measurements. Specimens of the 
same material, (1) in the form of rods were obtained 
and were heated and tested by the Newton ring method 
over the range 0° C. to 300° C.; and (2) in the form 
of tubes, which were tested by the Fizeau method over 
the range —20° C. to 150° C. The difference be- 
tweer the axial and radial coefficients of the tube 
specimens had also been tested. The expansion of the 
silica rod gave results agreeing with the extrapolation 
of the curve representing the original observations 
between 300° C. and 1000° C. The silica rods showed 
at first some peculiarities due to intrinsic strain, but 
settled down into a cyclic state which could be repre- 
NO. 2303, VOL.- 92| 
NATURE 
467 
| sented over the range 0° C. to 300° C. by the formula 
1o' x mean coefficient 0° to t=78:0—8650/(t+175), but 
the variation of the coefficient with temperature. was 
rapid and peculiar over this range and could not be 
represented by a formula of the usual type. The axial 
expansion of four different specimens had been 
measured, and could be represented between —20° C, 
and 150° C., with a little divergence by the formula, 
1o'x mean coefficient 0° to t=29-:0+0:250t—0-000701", 
which agreed over this range with the formula found 
for the rods, but was inadmissible for extrapolation 
to 300° C. The difference between the radial and 
axial coefficients was tested. Differences of the order 
of 5 or Io per cent. in the expansion in different 
directions appeared to be persistent, and were not 
removed by heating the specimens to 1000° C. or 
cooling in liquid air. It was concluded that the differ- 
ences in the radial coefficient might be due to distor- 
tion of the ring. It was considered that the most 
probable result for the cubical coefficient would be 
obtained by assuming it to be three times the 
linear. Owing to the smallness of the ex- 
pansion of silica, and its comparative freedom 
from hysteresis, the possible uncertainty with 
the silica bulbs was probably less than 1 in 1000, 
in spite of the imperfect annealing.—F, J. Harlow: 
The thermal expansions of mercury and fused silica. 
A more complete set of observations of the relative 
coefficients of expansion of mercury in silica than 
those previously published are obtained by the use of 
an electrically heated oil bath. The observations 
comprise readings at frequent intervals up to 300° C., 
and are in good agreement with the earlier observa- 
tions. Tables are included giving representative ob- 
servations and the final results. From the values of 
the coefficients of expansion of silica determined by 
Prof. Callendar, the coefficients of absolute expansion 
of mercury are calculated.—Prof J. A. Fleming: An 
experimental method for the production of vibrations 
on strings. An apparatus for the production of vibra- 
tions of strings loaded or unloaded was shown. The 
vibrations are produced on a string by attaching one 
end to the shaft of a small continuous-current motor 
of about 3 h.p. The other end of the string is 
attached to a fixed point which can be moved by 
means of a screw, in some cases a spring balance 
being interposed to measure the tension. When the 
motor is started the string has a circular motion given 
to its end which is equivalent to two simple harmonic 
motions at right angles to each other. If the tension 
is adjusted rightly the string then vibrates in sec- 
tions, and the number of sections can be adjusted. 
The distance from node to node can then be measured 
easily, and the frequency determined from the speed 
of the motor. In this way the velocity of the wave 
is measured,, and can be compared with the 
velocity determined by taking the square root of 
the quotient of the tension by the linear density of the 
string. This method is useful in studying the pro- 
perties of loaded strings. When the wave-length 
on the string extends over a distance of more than 
eight or ten loads, the string vibrates as if the loading 
matter were distributed uniformly, but the string 
cannot propagate vibrations when the half wave-length 
approaches equality to the distance between two loads. 
It is possible to show the reflection of a wave at a 
load placed at any point on the string, and also that 
this reflection is reduced by tapering off the loading. 
With this loaded vibrating string all the phenomena 
of inductive loading in telephone cables on the Pupin 
system can be imitated. 
Geological Society, December 3.—Dr. Aubrey 
Strahan, F.R.S., president, in the chair.—Dr. E. A. 
Newell Arber: A contribution to our knowledge of 
the geology of the Kent Coalfield. An account of the 
