1 



NATURE 



[May 4, ic>i i 



dull) Trik!) and illu«itrattHi journuK, tlii» »ubj>ri't it a» fresh 

 in the tnind«i of t^vcnbudy as it is fainiliur. It i» not 

 necessary ir •' ■ .im tu remark that th«! wild talk of 

 alinu!>i itici .U has very little foundation. liodie» 



move quicU:. „h in the air, and very often far too 



quickly, but what it generally overlooked i» that the 

 dilVu-ultv of the problem lie!> in the matter of supporting 

 the bo<]ly in the air rather than movinj^ through it, a 

 problem which is very n)uch simpler for land and water. 

 The It;;-- ■ ' >'ly itself, while of nhuul equal specific 

 gravit\ iti-r, i.s alKiut Moo times as heavy as air, 



and |ii .iken in conjunction with the motor and 



aer«.>piane, the Weight which has to be su|)t>orted is several 

 thou!>and times as heavy relatively to the air which it 

 displaces. Inasmuch as the support of the air necessitates 

 the use of an inclined plane and a corresponding expendi- 

 ture of energj', the sp«»eds made horizontally and independ- 

 ently of the wind have, at the present time, barely ex- 

 ceeded half the record speeds made on wheel vehicles. 

 As a matter of fact, only the other day the record 

 for passenger (light was broken by M. Nieuport at 

 Mourmelon, when he flew with two passengers for 

 ih. 4m. 58 1-5S., and covered 68-35 niiles at an average 

 sp«-ed of 63 miles per hour. It is difficult to say exactly 

 what the true record 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 1 have been able to 

 ascertain, by M. Nieuport on March 9 this year at Chalons 

 — (>8 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 ex- 

 ceeded 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, 

 however, 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 safetv in fly- 

 ing, 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 minutp< looking into the 

 question of these limits. 



The two chief things on which tli-' limit of speed in 

 locomotion will depend are : — 



(i) The motive power available. 



(2) The resistance, and the manner in which those resist- 

 ance's operate. 



But inasmuch as we are not merelv considering the 

 human body as a projectile, we do not take into account 

 such speeds as have b<'en attained bv man in such wavs 

 as, for instan.r, in a high dive, say.' of nearlv 100 miles 

 an hour, or v. n ilir thrilling descents such as are made 

 m a bobsleigh. \\V must really consider speeds which can 

 be made %vith safety; and there are two further questions 

 which arise : — 



(i) Knowledge as to possible obstacles, coupled with a 

 power of safely stopping within the distance to which our 

 knowledge extends, i.e. signalling and brakes. 



(2) Vibration. 



These two latter really limit conditions of high speed for 

 practical travelling. 



In daily life, the limiting conditions of speed in travel- 

 ling depend largely on the distance in which we can safelv 

 come to rest. .\s the population increases and there is 

 less room for everybody, the question of brake-power be-- 

 comes more and more important, and with it. of course, 

 the power of starting from rest quicklv. or. to put H in 

 scientific words, the power of rapidly effecting both positive 

 and negative acceleration. We are verv differently con- 

 structed from the particles of air in which we live, and do 

 not yet travel as fast, but fortunately, as vet. we are not 

 quite so crowded, since, according to Lofd Kelvin, thev 

 move about amongst each other at the ordinary atmo- 

 spheric temperatxire and pressure at an average speed of 

 ixoo miles an hour, and thev cannot avoid fewer than five 

 rnousand million collisions in every second. As you see 

 >n the streets, and as I shall show vou with regard to 

 NO. 2T'S6, VOL. 86] 



»uburl>an trafli< 

 a question of 



re and mor': 

 1 rememb' : 



can travel depend* upon tiie safe 



can stop. I can illustrate thU bv 



the donic of this building, which I 



it any injury, even when it is tn 



iHHir, if 1 have proper means for ininymj; u to r<s:. 1 



also drop a wineglass from the same height, and bring it 



I to re»t quite safely. 



' Owing largely to the perfection of the continuous brake, 

 the s|>eed lecords obtained on several railways are from 

 ()b to 98 miles an hour, which I have put down on the 

 diagram, and it is possible that 100 miles an hour ha* 

 been reached, and even exceeded ; but this is a very 

 different matter from the highest express running which 



is found really practicable. You m'" '■■ " '*'• ^•n*'^ 



chartv Fig. 3, a line indicating th< -ds 



of the fastest running (without s' en 



1 



MCTROPOl-lTAN - DISTRICT RAILWAY 



(maM«iON xOuSe TO CALINQ ) 





>. 1711 



principal railways of the country. The average distance of { 

 the quick runs is 517 miles, and the average fastest running 

 is 56-2 miles per hour. On either side of this line are the 

 two fastest speeds, namely, t>\\ miles per hour for 44} 

 miles on the North-Eastern Railway from Darlington fe» 

 York, and the lowest of these is 51 miles an hour, ov«r 

 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 conditions, 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 graphical 

 form the quickening in speed from the opening of the line 

 in i88o to the present time. You will notice that this 

 increase of speed has been followed by remarkable results; 

 the first immediate result is the possibility of a greater 



