Volume 4 of The General History of Astronomy, originally published in 1984, concerns the birth of modern astrophysics in the nineteenth century, the growth of astronomical institutions to around 1920, and the development of instrumentation. The volume commences in the 1850s, with the first astronomical applications of photography and spectral analysis. It closes in the 1950s, before the explosive growth made possible by new electronic devices and computers. In Part A, there are eleven chapters, written by an international panel of eighteen authors, on subjects such as observatories, large telescopes, astronomy in the southern hemisphere, and early radio astronomy. Intended for general readership, this book formed part of an in-depth synthesis of the development of astronomy from the earliest times.