640 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
inclined plane and a corresponding expenditure of energy, the speeds 
made horizontally and independently of the wind have, at the present 
time, barely exceeded half the record speeds made on wheel vehicles. 
As a matter of fact, only the other day the record for passenger flight 
was broken by M. Nieuport at Mourmelon, when he flew with two 
passengers for ih. 4m. 58$s., and covered 68.35 miles at an average 
speed of 63 miles per hour. It is difficult to say exactly what the 
true speed at present is round a course, but we may safely take it 
as probably under 70 miles an hour, the record being, so far as I 
have been able to ascertain, by M. Nieuport on March 9 this year 
at Chalons—68 miles 168 yards in the hour. 
We now see the relative position of the record speeds in the three 
elements on our speed chart (fig. 3), and it is obvious that while on 
land the speed has been far exceeded of the fastest animal, on water 
it has probably only recently surpassed that speed, while in the air, in 
all probability, it is still considerably below it. We must not, how- 
ever, from this argue that flying speeds will for safe flying machines 
rise so far beyond that of birds as land locomotion has risen above 
the speed of animals, for it looks as if the speed records on land 
would be at least equal for some time, if not greater, than that 
possible with safety in the air. At the same time there is no doubt 
that speed is the one great factor of safety in flying, and aerial speed 
records are sure to go on rising year by year, but time does not 
permit me to pursue this subject further to-night. 
Instead of vague surmises as to what may be done in the future, 
let us spend a few minutes looking into the question of these limits. 
The two chief things on which the limit of speed in locomotion will 
depend are: 
(1) The motive power available. 
(2) The resistance, and the manner in which those resistances 
operate. 
But inasmuch as we are not merely considering the human body 
as a projectile, we do not take into account such speeds as have been 
attained by man in such ways as, for instance, in a high dive, say, of 
nearly 100 miles an hour, or even the thrilling descents such as are 
made in a bobsleigh. We must really consider speeds which can be 
made with safety; and there are two further questions which arise: 
(1) Knowledge as to possible obstacles, coupled with a power of 
safely stopping within the distance to which our knowledge extends, 
i. e. signaling and brakes. 
(2) ‘VabmitiGn! 
These two latter really limit conditions of high speed for practical 
traveling. 
In daily life the limiting conditions of speed in traveling depend 
largely on the distance in which we can safely come to rest. As 
