408 REPORTS ON THE STATE OF SCIENCE, ETC. 
before (so that steel can be contemplated as the material of the new giant 
airships, although it has not been used hitherto); and lastly, since our 
whole construction has become more robust, we lessen the chance of acci- 
dental damage. This last is a factor which dimensional theory does not 
assess, but it is a very important one: whatever the scale of your airship, 
it will be flown by men of a constant size and of a constant clumsiness ! 
We have no recognized term to represent the capacity for damage which is 
latent in one standard air-mechanic and a large spanner; but it is a 
physical unit of very real significance, and it decreases in importance as 
the ship becomes more robust. 
Influence of Scale on Speed. 
23. So far, we have not considered the question of speed, or (what is 
the same thing) of endurance. Herbert Spencer pointed out another 
advantage which is possessed by the aquatic animal, in that the larger it 
crows the greater is the speed at which it can travel ;!* it is not, like our 
larger bird, obliged to travel faster, but it can. So with our bigger airship : 
if we double every dimension, its resistance at the same speed is increased 
by four, its petrol capacity by eight ; flying at the same speed it will have 
twice the endurance of the smaller craft,—that is, it can fly twice as far. 
The New Airships. 
24. Certainly we must take no unnecessary risk in planning the airships 
with which we hope to fly to India in 1927. Air Ministry policy in regard 
to lighter-than-air craft has fluctuated violently in the past, and although 
at the moment it is pressing on with their development, there seems little 
reason to believe that it has sufficient determination to resist the shock 
of another set-back like the loss of R.38. But greater size, as it seems to 
me, is not in itself an added risk at all. The R.38 disaster has left us faced 
with the necessity, unless we are content to take our problems abroad, 
of dispensing with previous experience; we must tackle this business from 
the very beginning, and trust to such intelligence as we can muster for its 
solution. So we do not make success more problematic—rather, less— 
when we depart from orthodox Zeppelin construction, of which we know 
little, in favour of steel, which we have used with success in aeroplanes 
for several years. We must design by theory, and in these larger ships 
we can employ a type of construction which lends itself better to theoretical 
treatment ; we must develop afresh the technique of girder construction, 
and by using stouter material we can employ more of the experience which 
we have already. 
It is my privilege to see a good deal of the Air Ministry design now 
in progress; and what gives me most hope of its eventual success is the 
completeness with which all concerned appear to recognize the magnitude 
of their undertaking. As someone put it recently, ‘The atmosphere 
generally is one of healthy cold feet’. We know that we have little 
experience in this country,—but we are determined to make up our 
deficit, so far as we can, by hard thinking and hard work; we know 
that our task would have been easier if airship research had been allowed 
12 Growth and Form, p. 22. 
