332 THE SCIENTIFIC PAPERS OF 



only 150 Ibs. up to 18 tons, and in all cases the results have been 

 most satisfactory." But he had received no other acknowledgment 

 from the Woolwich authorities ; and by degrees his connection 

 with the subject appeared to have been forgotten, thus furnishing 

 an illustration of Major Moncrieff's disappearing principle. 

 Major Moncrieff had also, in 18G8, recommended the use of 

 hydraulic resistance, coupled with air, instead of balancing weight, 

 in working out his beautiful principle, and this improved arrange- 

 ment had been modified again by the Elswick Company. The 

 discussion as to whether or not the recoil would always be 

 sufficient to bring the gun up to its position might be safely left 

 between the Elswick Company and Major Moncrieff. Prima facie, 

 it certainly ought to be sufficient. The gun in descending gave 

 off the whole force due to its descent to some reservoir which 

 might be provided to receive that store of force. In addition to 

 this there was the recoil ; and recoil and descending weight ought 

 surely to be sufficient to raise the gun to its original height. On 

 the other hand, it must be considered whether, in retarding the 

 descent of the gun sufficiently, it would not be necessary to 

 throttle the passages to such an extent as virtually to destroy the 

 surplus power. On this point practice alone could decide ; but, 

 certainly, the power itself, if it could be made available and be 

 stored up in a compressor, ought to be amply sufficient to raise 

 the gun again to its former height. 



In the discussion of the Paper 



"ON THE FIXED SIGNALS OF RAILWAYS," 

 By E. C. EAPIEE, 



MR. SIEMENS * said, it was now generally conceded that the 

 block and interlocking systems were conducive to the safety and 



* Excerpt Minutes of Proceedings of the Institution of Civil Engineers, Vol. 

 XXXVIII. Session 1873-1874, p. 225. 



