At length they paused before a low door, on which Bonny rapped in a peculiar manner. It was cautiously opened by a man who held a dim lamp over his head, and who evidently regarded them with suspicion. He was reassured by a few words from the young mate; the door was closed behind them, and, with the stranger leading the way, while Alaric, filled with curiosity, brought up the rear, all three entered a narrow and very dark passage, the air of which was close and stifling. [TO BE CONTINUED.] [Illustration: THE SPEEDWAY AS IT IS TO-DAY, LOOKING TOWARD HIGH BRIDGE.] BUILDING A BOULEVARD. BY J. PARMLY PARET. A few years ago the people of New York decided that they must have a new boulevard, where fast horses could be driven without running over people or upsetting the carriages of those who didn't want to drive so fast. They puzzled their heads for some time to find a suitable spot for their new driveway, and it was many months before they finally agreed upon the bank of the Harlem River which runs along the east side of the city. The shore here is straight for several miles, and is lined with such steep, wooded bluffs that all the bridges cross the river high up in the air. Here there is no danger of interruption, and as the roadway can be both straight and level, it was chosen as an ideal spot, and the Harlem River Speedway is now being built there. The building of this great boulevard has already been going on for two years, and it will probably take fully two more to complete it. The steep banks sloped down to the very edge of the river, so it was necessary to build the road out in the water for most of its length, and the workmen had to make land to build it on. In one or two places great masses of rocks were in the way, and here they cut the driveway right through the solid rock. At one point there was a big gap in the cliffs, and the road was built up on top of a high stone wall for over a quarter of a mile, while in another place they had to blast out thousands of tons of rocks from under the water to make room for the new drive. [Illustration: LEVEL STRETCH OF THE SPEEDWAY, SHOWING CRIBS, DREDGES, AND PORTIONS OF THE RIVER THAT MUST BE FILLED IN.] Long before they could begin the actual work of building such a big road as this the civil engineers spent many months preparing their "plans and specifications." They estimate so many hundreds of thousands of cubic yards of mud to be dredged out of the river bed; so many thousands of feet of crib-work to be built; so many hundreds of yards of stone wall to be built; so many cubic yards of filling and grading, and so many--well, so many other things to be done that it took a big printed pamphlet to mention them all. Then the contractors who wanted to build the driveway made their offers to do the work, and the contract was given to the lowest bidder. This is the way with all public improvements.