TRAVELING AT HIGH SPEEDS—HELE-SHAW. 641 
the population increases and there is less room for everybody, the 
question of brakepower becomes more and more important, and 
with it, of course, the power of starting from rest quickly, or, to put 
it in scientific words, the power of rapidly effecting both positive 
and negative acceleration. We are very differently constructed from 
the particles of air in which we live, and do not yet travel as fast, 
but fortunately, as yet, we are not quite so crowded, since, according 
to Lord Keivin, they move about amongst each other at the ordinary 
atmospheric temperature and pressure at an average speed of 1,800 
miles an hour, and they can not avoid fewer than 5,000 million col- 
lisions in every second. As you see in the streets, and as I shall 
show you with regard to suburban traffic, high speed is becoming 
more and more a question of starting and stopping rapidly. I 
remember in the early days of cycle racing, in order to lighten the 
machine, the racing men had no brake, until they found what is now 
well recognized—that the speed at which you can travel depends 
upon the safe distance in which you can stop. I can illustrate this 
by dropping an egg from the dome of this building, which I can do 
without causing it any injury, even when it is traveling at 30 miles 
an hour, if I have proper means for bringing it to rest. I also drop 
a wineglass from the same height and bring it to rest quite safely. 
Owing largely to the perfection of the continuous brake, the speed 
records obtained on several railways are from 96 to 98 miles an hour, 
. which I have put down on the diagram, and it is possible that 100 
miles an hour has been reached, and even exceeded; but this is a very 
different matter from the highest express running which is found 
really practicable. You will see on the speed chart (fig. 3) a line 
indicating the average railway speeds of the fastest running (without 
stopping) for the 15 principal railways of the country. The average 
distance of the quick runs is 51.7 miles, and the average fastest run- 
ning is 56.2 miles per hour. On either side of this line are the two 
fastest speeds namely, 614 miles per hour for 447 miles on the North- 
eastern Railway from Darlington to York, and the lowest of these is 
51 miles an hour, over the 51 miles from Victoria to Brighton on the 
London, Brighton & South Coast Railway. This shows how little 
the high speeds of all the railways of this country differ from one 
another, and indicates, at any rate for the present conditions, the 
highest speeds of traveling found suitable to our wants. 
I will take as another illustration of actual traveling the case of 
suburban traffic; and we have only time for one example, namely, 
the traffic from the Mansion House to Ealing on the Metropolitar 
& District Railway, the details of which have been kindly provided. 
by Mr. Blake, the superintendent of the line. Figure 5 shows 
38734°—sm 1911——41 
