Final answer:
The iron framework supporting a glass skin refers to the early technology that led to modern skyscraper construction. This technological breakthrough can be traced back to the Crystal Palace, the first significant example of iron and glass construction, and represents a forerunner to the steel-frame skyscrapers pioneered in Chicago in the 1880s.
Step-by-step explanation:
The iron framework supporting a glass skin was indeed a forerunner of modern skyscrapers. Such a structure was first prominently showcased in the Crystal Palace, designed by Joseph Paxton for the Great Exhibition of 1851. The Crystal Palace's use of vast amounts of glass supported by structural metal marked a significant shift in architectural design and foreshadowed Modernist architecture's trend towards industrially-produced materials like iron, steel, and sheet glass. Consequently, new architectural techniques emerged wherein buildings utilized steel frames that allowed for higher structures, such as those demonstrated by the works of William Le Baron Jenney and Louis Sullivan in Chicago during the 1880s and thereby facilitating the rapid proliferation of skyscrapers.
Rather than utilizing solid masonry cladding, which exudes a sense of solidity and reliability, these early skyscrapers employed a framework that allowed for a more daring expression of architectural design with the use of glass facades. As the Industrial Revolution rolled out more machined products and materials, it influenced modern architecture to adopt an aesthetic that embraced the strength and malleability of steel, paving the way for the glass-clad skeletons of today's high-rise buildings.