Locomotives have long been the subjects of photographic study. The earliest images are believed to be Daguerreotypes from the early 1850s. As early as the 1860s, locomotive manufacturers routinely photographed locomotives to document their construction and to help interest prospective buyers. The nature of the steam locomotive meant that a great deal about the machine could be gleaned by studying it from the outside. Railway enthusiasts were enamored with locomotives from the very beginning; sketches and drawings of engines date to the earliest days of railroading, while railway enthusiast photography certainly dates to at least the 1890s, if not earlier. While I’ve always been fascinated by railways, I didn’t routinely examine locomotives on film until I was about ten. My earliest railway photography tended to feature signals. If there were any locomotives in my pictures, these seemed to appear on the horizon in the form of a looming headlight. Later, I made a great many images of locomotives, sometime picturing them at work, other times resting between jobs, and often I examined them on a macro level; in other words, up-close and in detail. I’ve written a number of books on locomotives, and these chronicle their evolution and development, intended application and service, and performance. My body of locomotive photography has aided in illustration of these efforts. This selection of images is intended as the first installment in Tracking the Light of my exploration of locomotive geometry: the shapes of the machines. Later installments will focus on specific railway fleets, individual types, and perhaps some individual machines.