JuLy 25, 1912} 
NATURE 
545 
which the camber of the upper surface was about 
{in ro. It was found that the ratios of lift to drift 
were practically unaltered by the change of camber 
in the lower surface, but the lift coefficient at a given 
angle of incidence increased steadily with increase of 
camber, the gain in lift amounting to about 17 per 
cent. for a lower surface camber of 1 in 16, as com- 
pared with a plane under surface. ; 
Other Experiments in Connection with Aéroplanes. 
—Mr. O’Gormanm: has placed before the committee a 
considerable programme of further experimental work 
on aéroplane models, in relation to questions which 
have arisen in connection with constructional work 
proceeding at Farnborough. A scheme for further 
work has been approved by the committee, and this 
will be proceeded with as rapidly as circumstances 
permit. The committee held that the necessity of 
advancing more rapidly with these experiments ren- 
dered imperative the provision of another air channel; 
and, as already stated, it has been arranged to build 
a channel of section 63 ft. square, for which provision 
will be made by the Treasury. The increased accu- 
racy in measurement which it is hoped to attain by 
improved design in the reconstruction of the four-foot 
channel will also, if realised, appreciably increase the 
rate at which experimental data can be obtained. 
Effect of Blade Area and Pitch on Propeller 
Efficiency. At a constant translational. speed, the 
departure from maximum efficiency is negligibly small 
over a fair range of blade widths, from about 34 to 
48 in. The change of thrust under thé same con- 
ditions is also small. 
Tests have also been made on two series of pro- 
pellers of different blade widths, in which the pitch 
was varied somewhat on either side of that obtaining 
in the original design. Some effects of increase in 
pitch may be inferred from these experiments; with 
the wider blades an improvement in efficiency was 
obtained with the increase in pitch, and in the experi- 
ments made the limit of improvement did not appear 
to have been reached. With the narrower blades the 
maximum efficiency obtained was for a ratio of pitch 
to diameter of about 080. The investigation of the 
effect on the efficiency of variation in pitch will be 
continued. 
Experimental Work on Full-sized Aéroplanes.—It 
was mentioned in last year’s Report that arrange~ 
ments had been made for conducting full-scale experi- 
ments. These were commenced early in 1911 under 
the direction of the superintendent of the Royal Air- 
craft Factory. The earlier work was directed to the 
determination of the effect of various modifications in 
an existing machine. An aéroplane of Farman type 
was available for the purpose, and the alterations 
made aimed at diminution of head resistance by 
various means; the increase of mechanical efficiency 
by improvement of propeller design and correct cor- 
relation of propeller and engine; improvement in the 
design of the wings; increased ease of control; and 
improved directional stability. In all these respects 
satisfactory results have been attained; the alterations 
have effected a marked improvement in ease of con- 
trol, stability and speed, with increase of available 
lift. In connection with this work a standard form 
of ‘‘speed-resistance’’ and  ‘‘speed-horse-power ” 
curves has been adopted for setting out the qualities 
and performances of aéroplanes. This has been found 
very convenient for purposes of design. 
Attention is also being given to the problem of 
obtaining during actual flight measurements of the 
principal quantities affecting the behaviour of the 
machine, a knowledge of which is necessary. to 
enable the conditions of flight to be accurately 
analysed. Apparatus has been designed for record- 
ing the propeller thrust on machines in flight, and 
NO. 2230, vot. 89] 
measurements are also being made of the relative 
wind velocity and the gliding angle, while the effect 
on the stability of modifications in design is being 
specially studied. 
Meteorological Work.—In April, 1911, the Lords 
Commissioners of H.M. Treasury sanctioned” the 
establishment, by arrangement with the War Office, 
of a branch of the Meteorological Office, in connection 
with the Royal Aircraft Factory, at South Farn- 
borough, to supply meteorological information to those 
engaged in field work, and to carry on the investiga- 
tion of the upper air for the Advisory Committee 
under the direction of the Meteorological Office. Mr. 
J. S. Dines was appointed by the Meteorological 
Committee as meteorologist in charge of this branch 
office. Suitable accommodation for this experimental 
observatory was included in plans prepared for addi- 
tional buildings at the Aircraft Factory. 
This new branch of the Meteorological Office, for 
which accommodation is to be provided during 1912, 
is designed to fulfil three functions :— 
(1) To supply meteorological information and fore- 
casts in a form directly applicable for the guidance of 
airmen. 
(2) To carry on the experimental work for ‘the 
Advisory Committee. 
(3) To act as an observing station for the Meteoro- 
logical Office. 
Vertical Motion in the Air.—Experiments on vertical 
air currents have been carried out during the past year 
by means of balloons tethered to a point on a steel 
tower 95 ft. above the ground, with a view to the 
determination of the angular deviation from the hori- 
zontal of air currents at a moderate height. The 
method consists in following the motions of such a 
tethered balloon with a recording theodolite. The 
analysis of the records shows that the inclination of 
the wind direction to the horizontal does not normally 
exceed 20°, though on one occasion a downward cur- 
rent was observed making an angle of 43° with the 
horizontal, corresponding in this instance with a ver- 
tical component of the wind velocity of about eight 
miles an hour. As a rule, the larger deviations from 
the horizontal were not met with on days of strong 
winds. 
The Study of Gusts.—Some account was given in 
the previous report of the variation found in the gusti- 
ness of the wind at different levels. A comparison 
has been obtained during the past year of the gusti- 
ness at two points respectively 36 and 98 ft. above 
ground, the measurements being made by means of 
a pressure tube anemometer head. The gustiness at 
36 ft. was found to be about 30 per cent. greater than 
that at 08 ft., for the site where the experiments were 
made. r 
In connection with the work on vertical motion, 
records of wind velocity were taken with a more open 
time scale than is usual, and these have given some 
further information of value with regard to gusts. 
In a gusty wind of normal type, a rise of wind 
velocity is usually followed almost immediately by a 
fall of approximately eaual amount. In some of these 
observations, however, cases were found in which a 
sudden access of wind velocity persisted for at least 
one minute. Thus a case is recorded in which the 
wind rose suddenly from 13 to 23 miles per hour, 
followed by a slight fall and then a further rise to 
28 miles per hour; the wind remaining above 20 miles 
per hour for more than one minute after the first rise. 
Attention is directed to this special type of velocity 
change on account of the probability that similar 
phenomena, though possibly of greater intensity, in 
the upper air currents may explain one of the types of 
conditions known to airmen as “holes in the air.” 
Experiments in progress on the wind towers give 
