1!)11] on Travelling at Hi(ih Speeds on Surface of Earth. 1213 



These two latter really limit conditions of high speed for practical 

 travelling. 



In daily life, the limiting conditions of speed in travelling depend 

 largely on the distance in which we can safely come to rest. As 

 the population increases and there is less room for everybody, the 

 question of brake-power 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 Kelvin, they move about amongst each other at the ordinary 

 atmospheric temperature and pressure at an average speed of IHOO 

 miles an hour, and they cannot avoid fewer than five thousand milHon 

 collisions 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 recognised — 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 l)uilding, which I can do 

 without causing it any injury, even when it is travelling 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 fifteen principal railways of the country. The 

 average distance of the quick runs is 51-7 miles, and the average 

 fastest running is 56-2 miles per hour. On either side of this line 

 are the two fastest speeds, namely, 61|^ miles per hour for 44^ miles 

 on the Xorth-Eastern Eailway 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 and 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 con- 

 ditions, the highest speeds of travelling found suitable to our wants. 

 I will take as another illustration of actual travelling the case of 

 suburban traffic : and we have only time for one example, namely, 

 the traffic from the Mansion House to Ealing on the Metropolitan 

 and District Railway, the details of which have been kindly provided 

 by Mr. Blake, the superintendent of the line. Fig. 5 shows in 

 Vol. XX. (No. 105) k 



