The Rooftop Fire Escape: A Railed Bridge to the House Next Door

Connelly's invention "consists of a bridge surrounded by a railing and having openings in the ends of the floor thereof ... the said bridge being adapted to be placed on the roofs of adjoining or adjacent buildings, thereby permitting the ready and safe passage from one roof to the other." It further provides "alarms adapted to be operated from said bridge", whereby "the inmates of either or both of the said buildings may be alarmed". The bridge A has openings B at opposite ends of its floor, with guards C round them continuous with the side rails D. Placed so the openings are over the scuttles or trap doors, people pass up through one and "over the bridge to the opposite scuttle or trap door, being prevented from falling owing to the end guards and side rails". "Should said scuttle or trap-door not be open, the respective bell is rung, whereby the occupants of the house are alarmed or signaled", and they open it from within.

Stand two cardboard boxes 25 cm apart as neighbouring houses and cut a square hatch in each lid. Build a bridge from two dowel side rails and card decking, with a hole at each end over the hatches and guard rails round the holes, and glue it down. Load the middle of the bridge with weights until it sags visibly, measure the sag, and try a deeper side rail. Tie a small bell under one end that rings when a string across the far hatch is pulled.

**Anna Connelly** of Philadelphia filed US 368,816 on 13 May 1887; it is dated 23 August 1887. She claims a fire-escape bridge connectible with adjacent houses, with floor openings over their scuttles, guards and rails, and alarms operated from the bridge. **Honest limits.** Flow rates, crowd size and timber strength in the notebook are assumptions.