INDUSTRIAL REVOLUTION (CAMERA, STEEL)

The history of the camera can be traced much further back than the introduction of photography. Cameras evolved from the camera obscura, and continued to change through many generations of photographic technology, including daguerreotypes, calotypes, dry plates, film, and digital cameras.

Photographic cameras were a development of the camera obscura which uses a pinhole or lens to project an image of the scene outside upside-down onto a viewing surface.

Daguerre coated a copper plate with silver, then treated it with iodine vapour to make it sensitive to light. The image was developed by mercury vapour and fixed with a strong solution of ordinary salt (sodium chloride). Henry Fox Talbot perfected a different process, the

collotype, in 1840. Both used cameras that were little different from Zahn's model, with a sensitized plate or sheet of paper placed in front of the viewing screen to record the image. Focusing was generally via sliding boxes. Film allowed the movie camera to develop from an expensive toy to a practical commercial tool. Now a days, digital cameras now include wireless communication capabilities (for example Wi-Fi or Bluetooth) to transfer, print or share photos, and are commonly found on mobile phones.

The history of the modern steel industry began in the late 1850s, but since then steel has been basic to the world's industrial economy. Previously steel was very expensive to produce and only used in small expensive items such as knives, swords and armour. However the global steel industry has been going through major changes since 1970. China has emerged as a major producer and consumer, as has India to a lesser extent. Consolidation has been rapid in Europe.

Eads Bridge across the Mississippi River, opened in 1874 using Carnegie steel.