ON RAILWAY CONSTANTS. 205 



Reports on the Determination of the Mean Value of Railway 



Constants, 



NOTICE. 



The two following Reports, as well as the Report by Dr. Lardner on the 

 same subject, already publislied in the Reports of the British Association 

 for 1838, have been furnished in compliance with the request of the Com- 

 mittee to whom the superintendence of the experiments and the grants of 

 money for the purpose of ascertaining the amount of railway constants was 

 entrusted by the British Association. 



. The Committee originally appointed in 1837 consisted of Mr. H. Earle, 

 Dr. Lardner, Mr. Locke, Mr. Rennie, and Mr. Macneil, to these Mr. Edward 

 Woods was subsequently added. 



The engagements of the various members of the Committee prevented 

 them from giving that personal and individual attention to the experiments 

 which were so highly desirable, and but for the continued and indefatigable 

 exertions of Dr. Lardner, Mr. H. Earle, and Mr. E. Woods, the object of the 

 Association could never have been carried out. 



Of the two following Reports, the one is in continuation and conclusion of 

 that which has already appeared by Dr. Lardner ; the other is a separate 

 and independent Report by Mr. E. Woods, referring partly to the same and 

 partly to a great number of additional experiments. 



The Report of Mr. E. Woods, while it agrees in many important particulars, 

 differs in others from the Reports of Dr. Lardner, and, when viewed as a 

 whole, is somewhat different both in its structure and in the manner in which 

 the conclusions are arrived at, deduced, and reasoned upon. 



Under these circumstances, the Committee of the Mechanical Section of 

 the British Association at Plymouth were of opinion that the objects of the 

 Association would be best fulfilled by the publication of both ; the results in 

 which both agree will be looked upon as extremely valuable both by the 

 theoretical and practical man, while those in which they differ will form sub- 

 jects of great interest for future inquiry. 



Second and concluding Report on the Determination, of the Mean 

 Value of Raihvay Constants. By Dionysius Lardner, LL.D., 

 F.R.S., &c. 



By reference to the former part of this Report, it will be perceived that among 

 the points which remained for furtlier experimental inquiry the principal were 

 the following : 



1. Whether the presence of the engine and tender in front of the train has 

 any effect in rendering the resistance to the progressive motion of the train, 

 arising from friction or atmospheric resistance, or both of these combined, 

 less than it would be if the train were moved forward with the front of the 

 foremost coach presented directly to the air. 



2. Whether the ybrm of the front of the train produces any sensible effect 

 on the resistance, or whether any advantage can be gained by the adoption 

 of a pointed front like the bow of a ship. 



3. Whether, in moving down an inclined plane by gravity, the resistance 



