The Elder Pliny's Natural History is essentially a work of reference providing a wide-ranging account of human mores and achievement in the arts and sciences in the first century AD. It influenced the content and character of subsequent technical literature, but errors in transmission of the manuscripts led to undeserved criticism from the time of Niccolo Leoniceno, the late fifteenth-century Italian humanist. Pliny's work is here re-examined for the first time since the 1920s. Modern experiments, simulating the techniques described by Pliny, and an in-depth study of his development of a technical language, confirm his unique contribution to our knowledge of science in early imperial Rome. Pliny does not, in general, understand the principles underlying the phenomena he observes but makes a significant input - especially in the fields of crystallography, chemistry, and physics as well as of the applied sciences - from which beginnings those scientific disciplines would evolve many centuries later. Ironically, Pliny's scientific curiosity led to his death in AD 79 while observing the eruption of Vesuvius at close quarters.