PROCEEDINGS OP THE POLYTECHNIC ASSOCIATION. 



SLIDING CARRIAGES 



are used in the launches and on hoard the steamboats. 



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The recoil is controlled by compressing the slide between the bed and the 

 lower plate; for which purpose the bolts connecting- the upper and lower 

 pieces have a thread above, and a corresponding nut Avith handles. These 

 are set as firmly as the strength of an ordinary man allows, and will then 

 always suffice to keep the recoil within the limits of the slot in the slide. 

 After discharging the howitzer, the compression is relieved, and the piece 

 run out. 



In order that this arrangement may invariably perform its function, it is 

 necessary that the surfaces of the carriage, to be in contact, should be plane, 

 which will be known to be otherwise when the compression is not found to 

 be sufficient to control the recoil. In this case, dismount the gun, take the 



