Cantilevers Continued

I've just come across another article about the construction of the American Tract Society Building.  It included two photos of the great cantilevers, as they were being installed in the sub-basement:

The article discussed many details of the construction of the building.  It revealed this about the advanced derrick which was used: "The best test of the structure's capacity, which has been made, was when loads of 7, 6 and 5 tons were swung on three corners at the same time.  Lighter loads have been swung from all [five of] the booms at once."

Source:
The Railroad Gazette, vol 26, 14 Dec 1894, p850-852.