A short distance beyond this little caf lies the large bridge across the Meuse. Before the Germans arrived it was partly destroyed by the Belgians, but so inadequately that obviously the enemy could repair it easily. Bombs were therefore fired regularly from Fort Pontisse at the bridge, and only an hour ago it had been hit, with the result that a big hole was made in the undamaged part. In the road also big holes were made by the exploding projectiles. Having passed underneath the viaduct of the bridge, I found myself opposite Vis on the sloping bank of the Meuse. Two boys had been commanded by the Germans to work the ferry-30boat for them, and after I had shown them my passport, they took me to the other side.It is not proposed at this time to treat of the construction of machinery for transmitting power, but to examine into the conditions that should determine which of the several plans of transmitting is best in certain caseswhether belts, gearing, or shafts should be employed, and to note the principles upon which they operate. Existing examples do not furnish data as to the advantages of the different plans for transmitting power, because a given duty may be successfully performed by belts, gearing, or shaftseven by water, air, or steamand the comparative advantages of different means of transmission is not always an easy matter to determine.CHAPTER IIIAn apprentice may get a clear idea of this venting process by inspecting tubular core barrels, such as are employed in moulding pipes or hollow columns, or by examining ordinary cores about a foundry. Provision of some kind to 'carry off the vent,' as it is termed by moulders, will be found in every case. The venting of moulds is even more important than venting cores, because core vents only carry off gas generated within the core itself, while the gas from its exterior surface, and from the whole mould, has to find means of escaping rapidly from the flasks when the hot metal enters.
