RAILWAY CONSTANTS. 213 



single wagons was abont 11 '3 lbs. per ton. This difference 

 M. de Panibour ascribed to the atmosphere, yet it does not ap- 

 pear to have occurred to him to direct his experiments or cal- 

 cuhitions to the determination of the share which friction and 

 the air had respectively in resisting the motion. Having disre- 

 garded in all cases the effect of the velocity in modifying the 

 resistance, and having based all his calculations on suppositions 

 which are only applicable to friction, we must conclude, that 

 he regarded the effects of the air as so inconsidei-able, that, 

 without any error of practical importance, the mean retardation 

 due to them might be considered as part of the friction. 



It has been thought right to bestow some attention on the ex- 

 periments and calculations of M. de Pambour in this place, be- 

 cause they are not only the most extensive series of which we 

 have any knowledge, but because much stress is usually laid on 

 them by engineers and others who are interested in these ques- 

 tions. We shall, however, presently demonstrate that the re- 

 sistance of railway trains has so important a dependence on the 

 velocit}'^, that no principle of calculation can be admitted which 

 proceeds, like those of M. de Pambour, upon the supposition 

 of a constant amount of resistance. But we shall also be enabled 

 to give a conclusive proof, founded on direct experiments, that 

 the method of determining the resistance by the formula (18.) 

 adopted by M. de Pambour is altogether fallacious, and that by 

 such a method any value, however great, of the resistance might 

 have been obtained. 



Having noticed these erroneous conclusions to which M. de 

 Pambour has arrived, it is but justice to that gentleman at the 

 same time to acknowledge the activity and zeal with which he 

 pursued his inquiries, and the quantity of valuable results of his 

 extensive experiments by which he has enriched the practical 

 science of this country. That M. de Pambour should have over- 

 looked or underrated a source of resistance to locomotive power, 

 which, however obvious, had eluded the attention of the whole 

 engineering profession in Great Britain, as well as of his own 

 country, will not, we are sure, be felt by him to be any serious 

 disparagement to his sagacity. 



In commencing this inquiry, it was not suspected that that 

 part of the resistance which increases with the velocity, the 

 chief part of which, if not the whole, is probably due to the 

 atmosphere, formed so important an agent in opposition to the 

 moving power on railways worked at high speeds as the results 

 of experiments which were subsequently made have proved it 

 to be ; and in the acknowledgment of this oversight tlie writer 

 of this report very willingly joins. This source of resistance 



VOL. VII. 183S. p 



