Looking at Edinburgh Castle it is easily appreciated that it embodies a thousand year's worth of history. By investigation of soils and erosional features we can extend Edinburgh's history back to the end of the ice-ages and the movements of glaciers across the region can also be discerned. However, before the ice-ages we are confronted with a vast time gap of around three hundred million years. For this interval we can only surmise what local conditions in and around Edinburgh were like. It is when we investigate the bed-rocks that it is possible to take the story back further. Edinburgh's rocks, formed between 300 and 450 million years ago, afford startling perspectives of the extraordinarily different environments of those remote times. The sandstones with which much of the city is built, were washed down in rivers meandering through a tropical landscape. Coals from the seams of the Midlothian coal-field are fossil relicts of extensive rain-forests that thrived in steamy coastal swamps. The more visible rocks such as the famous Castle Rock, are memorials to volcanoes that erupted about 340 million years ago. Older than these, and dating back to more than 400 million years, are the Braid, Blackford and much of the Pentland Hills. Whilst the oldest rocks within a 25 mile radius of Waverley Bridge are tucked away in a few small patches of the Pentland hills. More than two hundred years of geological researches have left us with a remarkably detailed picture of the distribution of land and sea, of the climate and of the evolving plants and animals that lived here. 'Edinburgh Rock' is an account of these fascinating Palaeozoic times by Brian Upton and Euan Clarkson.