1884.] on Bicycles and Tricycles in Theory and in Practice. 19 



the means of obtaining healthy and pleasant exercise and of enjoying 

 to a certain extent the advantages which the bicycle affords. Thanks 

 to the perfection of the modern tricycle, cycling has become one of 

 the most popular institutions of the day. 



Whatever difficulty I may have had in doing justice to the 

 bicycle, the corresponding difficulty in the case of tricycles is far 

 greater. The number of makers and the variety of their work is so 

 great that it would be sheer madness on my part to attempt to 

 describe all that has been done. Those who wish to see the great 

 variety of detail which chiefly constitutes the difference between one 

 make and another must go to one of the exhibitions of these things 

 which are now so common. 



All I shall attempt will be an explanation of the leading principles 

 which are involved in the design of a tricycle. For this purpose it 

 will be necessary for me to mention occasionally some particular 

 machine ; but, in justice to the hundreds to which I cannot even refer, 

 I wish it to be understood that those named, though typical, are not 

 of necessity better than any other. 



It is first necessary to know what combinations of three wheels 

 will and what will not roll freely round a curve. The few possible 

 arrangements determine the general forms which a tricycle can take. 

 A wheel can only travel in its own dii*ection : no side motion is possible 

 without the application of considerable force, entailing strain and 

 friction of a most injurious kind. In any combination, then, of three 

 wheels each must be able, in spite of the united action of the other two, 

 to move in its own direction. There is on the table a model in which 

 the three wheels can take every possible position. To begin with, two 

 large ones are placed opposite but independent of one another and 

 parallel, and a small one parallel to the others is mounted between 

 them at one end. This arrangement rolls along in a straight line 

 with perfect freedom ; on twisting the plane of the third wheel it is 

 also free to roll round a curve whether the little wheel is before or 

 behind. If I shift the position of one of the large wheels so that 

 though still parallel to, it is no longer opposite, the other, then, though 

 they can freely move in a straight line, they can by no possibility be 

 induced to roll round a curve. It is clear, then, that two wheels which 

 are parallel cannot be employed in a tricycle unless they are opposite 

 one another. The only class of people who frequently appear to be 

 familiar with this fact are nursemaids, who always tip up the front of 

 a perambulator in turning a corner. If one wheel is in front of and 

 another behind a third, the combination can only freely turn a 

 corner w^hen the front and rear wheels are turned to proportionate 

 extents in opposite directions. The model is so arranged ; now, if either 

 of the little wheels is not turned to exactly the right amount they can 

 no longer roll, they can only be dragged round a curve. It is not 

 sufficient that two parallel wheels should be opposite one another : they 

 must be able to turn at different speeds. I have now the two large 

 wheels keyed on the same axle, so that they must of necessity turn 



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