Marcu 21, 1912] 
NATURE 
71 
THE NATIONAL PHYSICAL LABORATORY 
DURING tort. 
[eile annual meeting of the General Board of the 
National Physical Laboratory was held at 
Teddington on Friday last, March 15. As usual, a 
large number of visitors were invited to view the 
Laboratory, and were received by Sir Archibald 
Geikie, president of the Royal Society and chairman 
of the general board, and by Lord Rayleigh, the 
chairman of the executive committee. The visitors 
were glad to see that the director, Dr. Glazebrook, 
was sufficiently recovered, after his recent illness, to 
be able to take part in the proceedings. 
The continued development of the work of the 
laboratory has been well maintained during the past 
year. The William Froude National Tank was 
formally opened in July last. The Wernher building, 
erected, as its commemorative tablet states, by Sir 
Julius Wernher to advance the science of metallurgy, 
was completed in the autumn. A new laboratory has 
been provided, under a scheme approved by H.M. 
Treasury, to carry out tests for the Road Board on 
road materials and on experimental road-tracks. 
Other new buildings are now in course of erection. 
It was explained in the report of the Laboratory 
for the year 1910 that the control of the meteorological 
work carried out at the Kew Observatory had been 
transferred to the Meteorological Office. The testing 
of thermometers, telescopes, watches, and other 
instruments previously carried on * at - Kew—the 
i 
| 
observatory department of the Laboratory—was to be | 
continued there until the necessary accommodation 
could be provided. for the removal of the work to 
Teddington. The further buildings now under con- 
struction will enable this transference to be made. 
They include an optics section, which will provide 
space for all the optical work now carried out at Kew 
and Teddington, leaving room in Bushy House for 
other portions of the Kew work; and an administra- 
tion building, with offices, library, &c., and a section 
for the receipt and despatch of instruments. The 
need for such a building had become imperative, 
| against a 
thousandths of a millimetre. This method promises 
to be very accurate, and will appreciably lighten the 
work of obtaining the measurements. The first 
determinations of the ohm with the apparatus will, 
it is hoped, be made very shortly. 
An entirely independent method of evaluation of the 
ohm in absolute measure has been applied by Mr. 
Campbell. This is one of several methods he has 
suggested for the comparison of resistance with 
mutual inductance. An auxiliary condenser is tested 
resistance by Maxwell’s commutator 
method and against a standard mutual inductance 
and two resistances by Carey Foster’s method, the 
, results giving the ohm in terms of the mutual induct- 
ance, the value of which is calculated from its dimen- 
sions. Though not aiming at so high an accuracy as 
it is hoped may be attained with the Lorenz 
apparatus, the method appears to yield very good 
results. 
The photometry division has completed an interest- 
ing research on the visibility of point sources of light. 
The investigation was undertaken, at the request of 
the Board of Trade, in connection with the certifica- 
| tion of ships’ lights, which at a distance of two miles 
are seen simply as bright points of no perceptible 
angular magnitude. The unit of visible intensity 
adopted for comparison purposes is that of a point 
_ source of one-millionth of a candle-power one metre 
distant from the eye; this unit approaches the limit of 
visibility. An important point investigated was an 
apparently anomalous dimming of lights observed in 
the case of some persons using spectacles, which was 
found to be due to the chromatic aberration of the 
eye. 
In the course of the research on the fundamental 
| high-temperature scale in the thermometry division 
| Dr. Harker and Dr. Kaye. 
owing to the great increase in the activities of the | 
Laboratory. 
Towards the cost of these new buildings the 
Treasury will contribute the sum of 15,0001. The 
committee in its report explains that an additional 
sum of about 10,o0ol. will be necessary for the satis- | 
factory equipment of the buildings, and expresses con- 
fidence that the appreciation shown in the past of the 
national worl: done by the Laboratory will be con- 
tinued, and that the help needed will be readily forth- 
coming. 
The most interesting addition to the equipment 
completed during the past year, and shown in opera- 
tion on Friday last, is the Lorenz apparatus for the 
| interesting investigations have been completed. 
determination of the ohm in absolute measure. Some. 
particulars of this have been given previously. Much 
attention has been devoted recently to the elimination 
of the thermal electromotive force at the brush con- 
tacts, and with the form of brush finally adopted— 
annealed phosphor-bronze wires stretched as a bow- 
string and pressed on the circumferences of the discs— 
it is found that the desired result has been obtained. 
A further difficulty, the determination, with the high 
accuracy necessary, of the distance between the equa- 
torial planes of the coils, has been met by a special 
device. A light tubular magnet is suspended from an 
agate knife edge resting in an agate V, and swings 
like a pendulum; its rest-point can be determined as 
for a weighing balance. This magnetic pendulum is 
placed inside a coil, and the position for which there 
is no axial displacement when a current is passed 
some interesting ionisation phenomena have been met 
with, recently described before the Royal Society by 
The division has also: 
taken up the determination of the thermal conductivi- 
ties of heat insulators as used for cold-storage pur- 
poses, a subject of much practical importance. 
The metrology division has been largely occupied 
with the necessary work involved in the maintenance 
of standards, and with test work. The behaviour of 
the new silica standard metre is being very carefully 
followed. As in previous years, a number of investi- 
gations have been carried out for the Engineering 
Standards Committee. 
In the engineering department a large number of 
Dr. 
Stanton’s research on the effect of wind pressure on 
structures has been proceeding continuously almost 
since the date of the opening of the laboratory. The 
object of the work has been to enable a trustworthy 
prediction of the wind pressure on a large engineering 
structure to be made from laboratory experiments on 
a small model of the structure. The earlier parts of 
the work were concerned with experiments on small 
models in an air channel, which were compared later 
with the results of observations on larger structures 
in the natural wind. Following this, an attempt has 
been made to ascertain whether a trustworthy esti- 
mate of the total wind pressure over a large structure 
can be obtained from observations at one point. This 
work has recently been completed, and it is considered 
that sufficient data have been obtained to enable a 
prediction of the wind pressure over an area of several 
thousand square feet to be made from observations 
at a single point in the area. There remains the 
investigation of the more or less exposed nature of 
the site on the lateral variation of wind-force. For 
this purpose, permission has been received to make 
the observations on the Tower Bridge, and this worl: 
through the coil can be observed within about three ! will be commenced shortlv. 
NG» 2212, VOL. 89] 
