A STUDY IN LOCOMOTION. 



3 2 5 



this is to be regretted, for it gives a genuine interest to a journey, as 

 you may see by inspection of one of these graphics. 



The table which you see (Fig. 5) is prepared by engineers accord- 

 ing to the regulation progress of trains, a progress supposed uniform ; 

 we see, in fact, that the lines of progress are all straight, joining to 

 each other the two points which express the place and time of depar- 

 ture, the place and time of arrival. It does not then take into account 

 the real movement of the train, which is accelerated or retarded under 

 a great number of influences. The problem 

 which we seek to solve, that of a graphic ex- 

 pression of the real rate of a vehicle, supposes 

 that the carriage itself traces the curve of the 

 roads traversed in function of time. By means 

 of the apparatus which I present to you, and 

 which I call the odograph (Fig. 6), a wagon or 

 any kind of carriage traces the curve of its 

 movement with all its variations. 



This apparatus, based on the same princi- 

 ple as the Poncelet and Morin machine, is com- 

 posed of a tracing style which moves parallel 

 to the generatrix of a revolving cylinder cov- 

 ered with paper. The movement of the style 

 follows all the phases of that of the carriage, 

 but on a very reduced scale, in order that the 

 tracing of a distance of several myriametres fig. 6-Odorra f 

 may be contained in the dimensions of a sheet one third ofits diaraeter - 

 of paper. As to the movement of the cylinder, it is uniform, and 

 commanded by clockwork placed in the interior. In order that the 

 movement of the style may be proportional to that of the vehicle, 

 things have been so arranged that each turn of the wheel causes the 

 style to advance by a small quantity always the same. But as a turn 

 of the wheel always corresponds to the same distance accomplished, 

 the faster the vehicle travels the more turns will the wheel make in 

 a given time, and the more movements of progression will the style 

 undergo. This solidarity between the movements of the wheel and 

 those of the style is obtained by means of a small eccentric placed on 

 the vane. At each turn there is produced a puff of air which, by a 

 transmitting tube, causes a tooth of the wheel of the apparatus to 

 escape, and the style to advance by a small quantity. Similar effects 

 may be obtained by means of electro-magnetic apparatus. Thus the 

 swifter the vehicle goes the more rapidly will the line traced ascend ; 

 the comparative slope of various elements of the tracing will express 

 the variations of rate, as seen in Fig. 7. 



If we wish to learn the absolute value of time and distance, it is 

 sufficient to know that each minute corresponds to a millimetre counted 

 horizontally on the paper, and that each kilometre corresponds to a 



