312 Scientific Intelligence, ^c. 



Sir John Rennie, George Rennie, Esq., John Tavlor, Esq., Rev. 

 W. Taylor. 



Monday y 227id August. — Professor Moseley, " On certain points 

 connected with the theory of Locomotive Carriages." 



The author commenced by stating, that there were many gentle- 

 men present acquainted with the practical working of steam-engines, 

 but the relations between the theory and practice w^ere not perfectly 

 understood. The piston of a locomotive engine was pressed on either 

 side by two forces ; one resulting from the friction on the road, and the 

 other from the passive friction of the engine itself. If it was lifted 

 from the ground, a person endeavouring to move the wheels would 

 find a resistance equal to 150 lbs. ; the cause of the resistance was 

 this, that the traction upon the engine induced additional friction of 

 the machinery, and that probably was one-fifth of the whole amount 

 of friction. If the carriage moved without a train, there would be 

 a passive resistance ; if a train were attached to it, there would be 

 induced a considerable friction of machinery. There were, in fact, 

 three causes of resistance ; the friction of the carriage, the passive 

 resistance, the additional friction by the train ; the first and last 

 varying according to the weight of the train. On the other side 

 there was the expansive force of the steam. The quantity of work 

 done was greater as the velocity w^as less. He would chiefly apply 

 himself to inclined planes. Great power was required in drawing a 

 train up an inclined plane, but when the train came down the in- 

 clination, no additional power was gained, because the steam evapo- 

 rated through the safety-valve. On this account, in addition to the 

 loss of time, inclined planes on railways were highly injurious, and 

 should be avoided. 



Dr. Lardner would make a few observations . in consequence of 

 his having given evidence on this subject before Parliament. In all 

 inclined planes, which were more steep than the angle of repose, 

 there would be an unfavourable loss of power. The portion of 

 mechanical force used in ascertaining the inclined plane was not 

 repaid in the descent. If you could take advantage of the accumu- 

 lation of power in the descent, there might be a perfect mechanical 

 confirmation, but that was not the case in practice, because you were 

 obliged to check the velocity in the descent. It had been stated that 

 in his evidence he had said that inclined planes were not of im- 

 portance, as the friction in the ascent was given back in the descent. 

 That was an error ; he had not so said. Inclined planes were 

 injurious. All the experiments led to the conclusion that every 

 effort should be made to attain as level a line as possible. Every 

 departure from a level, though it saved a quantity of capital in the 

 construction of the road, entailed an everlasting expense. After a 

 number of experiments "he had made, the results were these ; that 

 in the ordinary state of the roads, the pressure necessary on a level 

 was 71bs. to a ton, but he had found an extraordinary difference 

 depending on the state of the rails ; a difference amounting, in some 

 instances, to such an extent that the friction was reduced to 41bs. ; 

 this occurred when it rained, and the rails were wet, but as soon as. 

 the rails became dry the friction again increased to7Ibs. He, there- 



