Bollman's separation from the B. & O. was not a complete one. The railroad continued its program of replacing timber bridges with Bollman trusses, and contracted with W. Bollman and Company for design and a certain amount of fabrication. There is some likelihood that eventually fabrication was entirely discontinued at Mount Clair, and all parts subsequently purchased from Bollman. The firm prospered, erecting a number of major railroad bridges in Mexico, Cuba, and Chile. Operations ceased from 1861 to 1863 because of difficult wartime conditions in the border city of Baltimore. Following this, Bollman reentered business as sole proprietor of the Patapsco Bridge and Iron Works. [Illustration: QUINCY BAY BRIDGE Figure 17.--CHICAGO, BURLINGTON AND QUINCY RAILROAD BRIDGE over Quincy Bay (branch of the Mississippi River) at Quincy, Illinois. The pivot draw-span was formed of two Bollman deck trusses supported at their outer ends by hog chains. The bridge was built in 1867-1868 by the Detroit Bridge and Iron Co., Bollman licensee. (Clarke, _Account of the Iron Railway Bridge ... at Quincy, Illinois_.)] The most noteworthy of Bollman's works in this period was a series of spans at Harpers Ferry. The B. & O.'s timber bridge had been destroyed by Confederate forces in June 1861, and the crossing was thereafter made upon temporary trestlework. This was a constant source of trouble, with continuing interruptions of the connection from high water, washouts, and military actions. The annoyance and expense of this became so great that the company decided to risk an iron bridge at the crossing. In July and August 1862, two sections of Bollman truss, spans no. 4 and no. 5 were completed. As this occurred during the time when W. Bollman and Company was inoperative, the work was produced at Mount Clair to Bollman's design and, undoubtedly, erected under his supervision. Five weeks later, on September 24, these and Bollman's famous Winchester span of 1851 were blown up by the Confederates, and the line's business was again placed at the mercy of trestling. The spirit of the B. & O. administration indeed seems to have been unshakable when, in the face of such heartbreaking setbacks, it determined to again bridge the river with iron, even at the height of the hostilities. In November, span no. 5 was erected, and by April 1863 nos. 3, 4, and 6 also. These were the four straight spans in midriver between the "wide" (or "branch," or "wye") span and the span on the Maryland shore over the Chesapeake and Ohio Canal (see fig. 13). Although the wood floor system of these spans was burned for strategic reasons by U.S. troops later in 1863, they survived the war.