In fastening the two long lines of rails, the profession of track-laying rises to almost supreme heights. The men who fasten the rail with angle iron and a single roughly-adjusted bolt in each rail-end are head-strappers and past masters in their art. After them in due season come the back-strappers, finishing that fine work of solidly bolting the rail against the vast strain of a thousand-ton train being shot over it at lightning speed. And after the back-strappers and the men who have spiked the rail to the ties, comes the locomotive itself, bringing more ties, more rails, more angle-bars and bolts, and more spikes to the front. Then sometime later the road-bed is ballasted and the line made ready for heavy operation. But track-laying is frequently machine systematized these days; and in this, as in so many smaller things, the mechanical device has supplanted the man. A real giant is the track-laying machine. It is mounted upon railroad tracks and is a form of overhead carrier with a tremendous overhang. The carrier is fed with the cross-ties from supply cars just back of the machine and the ties are dropped, each close to its appointed place, as a locomotive slowly pushes the entire apparatus forward. In a smaller way the heavy steel rails are delivered from under the overhang of the carrier. A gang of men make short work of the fastening of the rail to the cross-ties and the machine moves steadily forward. It has been known to make two miles a day at this work. * * * * * Culverts have been laid for each small run or kill or creek; the bridge-builders along the new line finish their work and cart off their kits; the day comes when there is an unbroken railroad from one end of the new line to the other. It links new rails and new towns; its localities produce for new markets, commerce from strange quarters pours down upon the land that has known it not. Passenger trains begin regular operation, the fresh-painted depots are brilliant in their newness, the shriek of the locomotive sounds where it has never before sounded. Life is awakened. The railroad, which is life, has reached forth a new arm, and creation is begun. CHAPTER IV TUNNELS THEIR USE IN REDUCING GRADES--THE HOOSAC TUNNEL--THE USE OF SHAFTS-- TUNNELLING UNDER WATER--THE DETROIT RIVER TUNNEL.