But it is when the railway emerges from the Everglades that the most wonderful part of the undertaking is seen. A chain of some 30 verdant islands, composed of coral limestone, stretches out in a graceful curve for about 109 miles, to disappear finally into the depths of the Gulf of Mexico at Key West. These reefs are separated by channels of open sea, of varying widths. These interruptions to the continuity of dry land are spanned by massive arched viaducts wrought in masonry. Where the line traverses the islands themselves the permanent way either is carried on embankments or through deep cuts. The expensive bridging has been reduced to the minimum, however, for in some cases where the water is shallow the islands are linked together by a massive solid earthen embankment. This section of the railway may be said to be amphibious in the full sense of the word. In fact, at one point the passenger in the train is carried beyond the sight of land. The engineer had to build his structure sufficiently strong and solid as to combat the forces of wind and wave, and at a level beyond the reach of the spray. When it is remembered that the railway runs through a territory where tropical storms of terrific fury prevail, and where cyclones are continually wreaking widespread damage, some idea of the character of the work requisite to withstand the buffetings of these abnormal visitations may be gathered. These climatic disadvantages were brought forcibly before the moving spirit in the enterprise at the time of its conception, and accordingly he demanded that the bridge-work should be built as strongly as engineering science could make it. No expense was to be spared, for the financier was determined that no apprehensions as to safety should be permitted to lurk in the mind of the timid traveller. The engineer took him at his word. The depth of water in which the viaducts are built ranges from 10 to 15 feet and more, while the rails are laid 31 feet above low water. At some places the channel is wide enough to float a large steamship. The viaducts have been carried out in ferro-concrete, wherein the masonry is strengthened by means of iron rods, freely intersecting, which serve to bind the whole mass into a solid, homogeneous whole, so that the viaduct from end to end becomes practically a single, monolithic structure.