JANUARY 12, 1912] 
turbations of the atmosphere which are 
of limited extent and duration. To-day the 
most needed improvements in aeroplanes 
are stability in wind-eddies and safety in 
landing. 
The meteorological phenomena causing 
these difficulties are discussed here at some 
length because their solution belongs to 
mechanical science and therefore merits 
the attention of our best engineers. 
There is an erroneous idea that the 
aeroplane has been developed without lab- 
oratory experiments and that a study of 
the theory of flight, and hence the science 
of aviation, does not require theoretical 
knowledge of the different factors which 
influence it. The pioneers in aviation, 
Lilienthal, Maxim, Langley and _ the 
Wrights, experimented in the laboratory 
with surfaces exposed in wind-tunnels and 
on whirling-tables, and the best shapes for 
balloon-envelopes to present the minimum 
resistance to propulsion were also obtained 
from models. Theoretical knowledge based 
on experiments is indispensable to the 
aeronautical engineer as distinguished 
from the aviator. Only on such a founda- 
tion can we build up the new science of 
aeronautics and a-technology which is in- 
dispensable for the development of this 
new branch of engineering. 
M. Eiffel, the distinguished engineer, in 
describing the results of his recent work in 
aerodynamics says: 
It must be admitted that the experiments in 
the laboratory with small models can furnish data 
useful to aeronautical constructors, saving them 
both money and time in experimenting, For a 
series of laboratory experiments made on model 
. aeroplanes, or on wings of small size, which can 
be quickly and surely modified, gives the basis for 
later computation, either for the section of the 
different members depending on the strength of 
the material used, or for the conditions of equilib- 
rium and stability, having regard to the calculated 
or assumed weight for each member. The same 
thing applies to a model of a screw-propeller 
SCIENCE 
balloon, La France. 
43 
which tried under proper conditions may give in- 
formation about the action of the actual propeller. 
The experiments with full-sized aeroplanes are 
almost always disturbed by wind, which introduces 
very large causes of error, and the trials being 
made necessarily with new apparatus of uncertain 
operation are generally dangerous. On the other 
hand, laboratory experiments can be conducted at 
any time and under different conditions and their 
results enable the knowledge of the engineer to 
replace the inspiration of the constructor, which 
in new fields may sometimes lead to fortunate dis- 
coveries, but may also give rise to costly mistakes. 
The establishment of aerodynamical lab- 
oratories, therefore, marks the entrance of 
aeronautics into the domain of engineer- 
ing. Probably the first of these was or- 
ganized by Captain, later Colonel, Charles 
Renard at the Central Establishment for 
Military Aeronautics at Chalais-Meudon, 
near Paris, about 1884. Here important 
investigations on light motors and the re- 
sistance of bodies of different shapes to mo- 
tion through the air were conducted, which 
resulted in the first successful dirigible 
Experiments upon 
lifting screw-propellers, with a view to 
aviation, followed, and Colonel Renard 
carried on similar work until 1903, when 
he was succeeded by other officers and the 
name of the laboratory changed. 
Important experiments on the resistance 
of the air to falling bodies were made be- 
tween 1903 and 1906 by the eminent con- 
structor of the Eiffel Tower there and later 
at his laboratory provided with a large 
wind-chamber on the Champs de Mars. Of 
great importance are the determination of 
the relations between the velocity and pres- 
sure of the air on a normal plane and upon 
plane and other surfaces at varying angles 
of incidence, the distribution of the pres- 
sure over the surface and the tests of aero- 
plane-wings. The results of the experi- 
ments have been published in two large 
volumes with the detail and elegance char- 
acteristic of M. Hiffel. 
