170 



* KNOWLEDGE . 



[Sept. 14, 1883. 



to take any note of a thing that creeps along at the rate of 

 four miles an hour and has toy wheels. 



To a rider of even average strength there are very few 

 hOls that need be walked, and those only the very steep 

 ones, and it is a mistake to inculcate the impression that 

 one mile in ten has to be walked. I have a great regard 

 for Mr. Browning, but feel compelled to endeavour to set 

 aside such fallacies as this, as I think they must serve as a 

 deterrent to would-be cyclists. 



The fact that Mr. Broioning Jinds tltis to he the ease is in 

 itself enoi'gh to condemn the ti/pe of machine he advocates, 

 as it is certainly not my experience, nor is it the ex- 

 perience of anyone I know, neither will it be the experi- 

 ence of anyone who possesses even an ordinary amount of 

 strength. 



I know an aged clergyman, very nervous and very 

 feeble. When he first commenced to ride, he, of course, 

 found it rather trying to ride the steepish hills in the north 

 of London, but now he goes on his way, and very seldom 

 walks up any but the very steepest of hills. 



Anyone who wishes to begin to ride a tricycle will 

 inevitably ere long strive to improve his pace, no matter 

 how meek his preliminary aspirations may be ; Vjut if he 

 starts with a very small wheel he will never be able to 

 improve his speed, but will be a perpetual snail along the 

 road until he goes to the further expense of a new machine. 

 If, on the other hand, he at the outset goes in for a 

 machine that will travel fast at pleasui-e, he can ride it as 

 fast as he pleases or as slow as he pleases. 



It follows as a mere matter of course that a machine that 

 can he driven at a very high rate of speed must from that 

 very fact he an easy running machine, as otherwise it 

 could not be driven at a fast speed. Therefore, this is the 

 machine to select, and while going slowly the utmost ease 

 of propulsion is existent ; and it is, at the same time, 

 always possible to improve the speed as experience is 

 gained. 



To recapitulate, a fast machine imi&t ipso facto be an easy 

 machiue to propel. 



I fully endorse Mr. Browning's view as to lightness, as I 

 have always urged this as a sine qua non — i.e., for a not too 

 heavy rider, and I myself ride an Imperial Club which 

 weighs under 60 lb., and yet it has -50 in. wheels. This 

 machine is geared up to a 60 in., and still I ride all the 

 hills I come to, seldom or ever dismounting ; and I have 

 several times ridden nearly, and even over, 100 miles a 

 day. This machine is as easy to drive and as fast as a 

 bicycle, and I can always hold my own on the road with 

 anything, and yet when simply riding slowly I can move 

 along with the slightest possible exertion. 



Nothing wearies so much as rapid pedalling, and nothing 

 looks so ungraceful ; and it is obvious that with small 

 wheels the pedalling must be very rapid indeed to get any 

 pace at all. With my machine, however, my feet pass 

 very slowly round and round, and still the gearing up 

 (which, of course, consists in having the lower chain 

 wheel larger than the top one ; so that the wheels go 

 round faster than the feet and the pedals) always keeps 

 up a fair pace, and this is attained without fast 

 pedalling. 



The machine that I am sure will give the best result will 

 be one weighing little, and that has wheels no less than 

 48 in. in diameter, and if this be fitted with the recently- 

 perfected " speed-gear," either a fast speed or a low speed 

 can be used for the level or for mounting hills, as the case 

 may be. 



I fear that I have already trespassed too far upon your 

 space, but there are several other points which might have 

 been dilated upon for the advantage of your readers, many 



of whom are absolutely certain to " go in " for tricycles 

 when they realise how extremely useful they may be made 

 for exploring the country and for means of exercise. 



Sigma. 



WIXDS AS PROJECTILES. 



MJ. C. HOUZEAU, referring to observations on 

 • the formation of clouds made b\- jM!M. Lancaster 

 and Tempel, and by Mr. R. T. Armstrong, communicates 

 to Ciel et Terre an article on " The Nature of Wind." He 

 remarks that although wind is air in movement, the move- 

 ment cannot be likened to that of a liquid sheet of vast 

 extent, nor to that of a vein of liquid, nor to that of the 

 sea- waves. If the air flow were in vast continuous sheets, 

 its pressure would only vary slightly and gradually over 

 the area it acted upon. It would not exhibit abrupt 

 changes and intermittences. The aspect of a field of 

 wheat on which the wind blows suffices to show that the 

 air neither moves as a sheet nor as a vein. 



In squalls there is often complete repose between the 

 blasts. On Nov. 11, 1878, M. Houzeau witnessed a 

 remarkable instance of this about 200 kilometres south of 

 the Lizard. The pufTs were of extreme violence, w-hile in 

 the intervals the air scarcely moved. These intermittences, 

 although reminding him of waves bursting on a shore, 

 could not be considered like them. Between two succeed- 

 ing sea-waves there is no water ; the hollow is filled with 

 air ; if it were occupied with the former fluid the inter- 

 mittence would give place to continuous action. Cut 

 between the wind blasts there is air, which is not carried 

 on with them. M. Houzeau does not deny that there is 

 often a general movement of translation of air, as a proper 

 motion, or as the result of blasts dragging it with them ; 

 but the phenomenon appears to him to consist of the move- 

 ments of detached masses, which, to give precision to the 

 idea, he compares with projectiles traversing the general 

 mass of the atmosphere. The limited area to which storm- 

 action is often confined, bending some trees violently and 

 not aflecting their neighbours, shows that these aerial 

 projectiles have little breadth. Another fact, he con- 

 siders, points to the same conclusion, for, if when 

 the wind is strong, its pressure per square metre 

 is observed on anemometers of dilTerent sizes, the 

 larger ones show the highest proportional results. The 

 greater the surface, the greater the chance of its receiving 

 the shock of the projectiles. If there were no divisions 

 in the air-streams, the pressure per square metre would be 

 independent of the dimensions of the anemometer plates. 



The friction of air is so slight that there is nothing 

 astonishing in the feeble entraining power of the pro- 

 jectiles. What is less easy to conceive is the nature of the 

 force which impresses upon sharply-defined portions of air 

 the furious velocities which sometimes animate them. But 

 before attacking this question Mr. Houzeau advises study- 

 ing what may be called the texture of the air in tempests, 

 and to ascertain the number, dimensions, and relative 

 spacing of these projectiles which traverse the atmosphere 

 as a kind of mitraille. 



If, as M. Houzeau states, it is a general fact in storms 

 that large anemometers show a much greater average pres- 

 sure than small ones, it is evident that calculations founded 

 upon the velocities of the cups usually employed give no 

 indication of the resisting power required to prevent a 

 recurrence of such incidents as the Tay Bridge disaster. 

 But M. Houzeau should indicate the experiments upon 

 which he bases this statement, as exactly the opposite is 

 affirmed by other persons. 



