The illustrations in old skyscraper marketing books tend to fall into two categories: pretty pictures of the exterior or main interior spaces, and construction photos. The pretty pictures are a traditional form of showing off architecture, and the construction photos were the 1900 way to show off high tech. The Broadway Chambers building’s book, because it is based on an exhibit run by engineers, has some internal details, including specifically spandrel sections that show the method used to support the masonry curtain wall from the steel frame.
As with all buildings of that era, the bulk of the facade masonry is common brick. There is always veneer as the outermost wythe: in most of the facade the veneer is ornamental brick, at the bottom it is stone, and at the top it is terra cotta. There is also terra cotta ornament sprinkled about on the facade, much of it colored. (You can see blue, pink, and yellow in the photo above) Since this is a true skeleton-frame building, all of the exterior wall is supported on the spandrel beams, but given the depth of ornament, some of the support details are a bit complicated. To go in the order of the illustrations in the book, here’s a model (at a large scale, possible full scale) of a portion of the top three floors of facade at the Paris Exposition:
That’s good for giving a sense of the facade to people who would likely never see the building. The next photo seems to be mislabeled. The caption says it’s the plaster model, but the model can be seen at the lower right in the photo above and it’s a white model of the general shape. This certainly looks like a photo of the top of the actual building:
Here’s the first of the spandrel-section models, at the transition from stone veneer to brick:
That can be a little difficult to read if you’re not familiar with these things, so here’s a crudely-colorized version:
The main structural element is the large built-up plate girder that is the spandrel beam, the I in green. To its left is an ordinary floor beam (as a green rectangle) and to its right is a bracket (red rectangle) holding a secondary exterior spandrel beam (the green channel). Those brackets and secondary beams are what support the large projecting stone water-table here. You can see the regular plane of the wall at the very top and bottom, right around the outboard flange tips of the plate girder. The plate girder and second beam support the main loads, but you still need supports for the soffits below the water table (the pair of red angles on the far right) and below the main beam/above the window below (the red angle at the very bottom). For comparison here’s the spandrel section one floor up, through the brick at a typical floor:
That’s an interior floor beam on the left and a double spandrel beam to support the 20-inch-thick brick masonry panel. Note the double angle at the bottom left. Another comparison, here’s the spandrel section at the water-table below the arcade at the top floors:
The spandrel beam is an I-beam and a channel, with three angles for additional support and bunch of steel-rod staples to hold the lightweight terra cotta in place. All to this became ordinary in the following two decades, and has become familiar again to people working on facade inspection and repair over the last forty years, but this was new and exciting in 1900.