ON RAILWAY CONSTANTS. 



215 



It appears, therefore, that the distance run with the wedge foremost dif- 

 fered only 80 yards in a distance of about eight miles from that through which 

 the same train ran with its flat front. This and the other differences indi- 

 cated in the table are evidently such only as would take place Avith the same 

 experiment twice repeated with the same carriages. 



With a view to ascertain how far mere magnitude of frontage, indepen- 

 dently of the general magnitude of the train, is productive of resistance, the 

 front of a coach was enlarged by boards extending from either side to a di- 

 stance of about twenty inches, adding about twenty-four square feet to the 

 front surface, and forming a sort of wings in front of the carriage, but no 

 corresponding Avidth being given to any other part of the carriage. The 

 coach thus prepared was placed at the summit of the Sutton plane, and al- 

 lowed to descend from a state of rest. It was then brought back to the sum- 

 mit and the wings removed, and was allowed to descend in its ordinary 

 state. The result of these two experiments was as follows : — 



From which it was inferred, that mere width of frontage, apart from the 

 general increase of magnitude, was not productive of any considerable prac- 

 tical effect in increasing the resistance. 



A strong impression existed in the minds of some engineers and scientific 

 men, to whom the results of these experiments was communicated while 

 they were in progress, that the shape of the hinder part of the train might 

 iiave an effect upon tlie resistance. It was supposed that in very rapid mo- 

 tion a tendency to a vacuum would be produced behind the train, and that 

 a corresponding atmospheric resistance, due to this partial vacuum, would 

 be produced in front ; that, consequently, if the square shape was removed 

 from the hinder part, less resistance would be found. Although no great 

 weight was attached to this, it was determined, nevertheless, to submit it to 

 a trial, and with that view a train of three carriages was placed at the sum- 

 mit of the Sutton plane, falling -^, and allowed to descend by gravity in 

 their ordinary state. They were next alloAved to descend, having the pointed 

 end behind ; they next descended with the pointed end before : and, lastly, 

 they were once more allowed to descend without the pointed end. The result 

 of these four experiments is given in the following table. (See Table, p. 216.) 



In the third column is expressed the entire distance run, in yards ; in the 

 fourth column is the time of going that distance ; in the fifth column is the 

 speed acquired in descending the Sutton plane ; in the sixth column the time 

 of descending that plane; in the seventh column the time of moving a di- 

 stance of 2\ miles from the time of starting ; and in the last column, the 

 time of moving from the twelfth to the twenty-eighth stake, throughout 

 which, tiie motion being tolerably rapid, the effect of the air might be ex- 

 pected to be greatest. 



It is evident, from these experiments, that no modification of the resist- 



