404 REPORTS ON THE STATE OF SCIENCE, ETC. 
as to induce him to take a ticket and go up himself,—it is not necessarily 
the feature on which you should lay most emphasis. 
Safety, comfort and reliability,—these are the true essentials. Until 
these can be guaranteed,—so long, that is, as the saving of time which travel 
by air should render possible is only problematic,—it will have attractions 
only for the few: given these, any saving of time over the older forms of 
transport will have its effect. Now high speed militates against all three, 
besides being very costly; the lower we can afford to make the top speed 
of an aeroplane, the lower will be its landing speed, on which, primarily, 
its safety depends. An airspeed of anything over 80 m.p.h., will suffice, in 
general, to achieve a saving of time over other forms of transport, especially 
when the journey is such that in the ordinary way delays are caused by 
customs’ examinations, etc. In relatively undeveloped countries very 
much less will suffice: indeed, the aeroplane or airship, once established _ 
as economic and reliable, will hardly have a competitor. Do not these 
considerations justify the Aeronautical Research Committee in its policy | 
of placing ‘ safety first’ ? Is it not wiser to aim at satisfying, rather than 
at creating, a demand ?] 
The Giant Aeroplane. 
15. Wildest of all aeronautical predictions are those which tell of the 
giant aeroplane. We must all have met, in the illustrated magazines, 
hair-raising descriptions of monsters which will carry the armament of a 
first-class cruiser. I fancy that these articles are easy to write,—although 
their illustrations must call for some ingenuity ; for they proceed on this 
simple argument: ‘ Already the size of aeroplanes has increased from the 
earliest types, just capable of taking one man to a height of two or three 
hundred feet, to monster troop-carriers which can transport twenty-five 
men, or more, complete with equipment. In another ten years we shall 
see an entire company of infantry carried in this way; in another fifty, 
a battalion’. 
Galileo and the Dimensional Handicap. 
Now a good fantastic story on the model of Jules Verne has attractions 
for most of us: itis this argument which we cannot allow to pass. The man 
who uses it believes, with a feeling of justifiable pride, that he is right in | 
the van of progress: he would be pained to learn that its foundations were | 
destroyed nearly 300 years ago, by a certain theoretically-minded | 
scientist named Galileo! Yet such is the fact: in a memoir published in 
1638, Galileo showed conclusively that (in the words of Professor D’Arcy 
Thompson) ‘ neither can man build a house nor can Nature construct an 
animal beyond a certain size, while retaining the same proportions and 
employing the same materials as sufficed in the case of a smaller structure ’.° © 
Its Operation in Nature. 
16. The demonstration is quite simple. Let us start with an ordinary | 
fox-terrier dog, and imagine that we are endowed with power to create — 
another of exactly twice the scale,—that is, twice the height, twice the - 
5 Growth and Form, p. 19. 
