79．Moreover，in addition to its being a transportation pathway equipped with amammoth physical plant of tracks signals，crossings，bridges，and junctions，plus telegraph and telephone lines, the railroad nurtured factory complexes，coat piles, warehouses，and generating stations，forming along its right of way whathas aptly been called “the metropolitan corridor”of the American landscape.

(the railroad nurtured factory complexes…为句子主干；what引导的从句作forming的宾语)

而且，铁路除了是装备有庞大的路轨信号厂、十字路口、桥梁、交叉点以及电报和电话线的运输路径外，还产生了联合工厂、服装大楼、仓库和发电站，在它的沿途形成了美国风景中被恰如其分地叫做“都市走廊”的景象。

解析：

主句：therailroad nurtured factory complexes…..

从句1：in addition to its being atransportation pathway

修饰成分1：equipped with a mammoth physicalplant of tracks signals，crossings，bridges，and junctions，plus telegraph and telephone lines,

修饰成分2：forming along its right of way

从句2：what has aptly been called “the metropolitan corridor”of the American landscape.

从句2修饰修饰成分2中的way

修饰成分2修饰了主句中的宾语factory complexes…..

修饰成分1修饰了从句1

从句1修饰主句中的主语the railroad