James Hutton was one of the great thinkers of the 18th century, living at the time of the Scottish Enlightenment alongside other famous Scots such as Adam Smith, Joseph Black and James Watt. Often called the ‘Father of Modern Geology’, Hutton carried out pioneering research on the formation of rocks, and it was this research that began our understanding of the age of the Earth. His observations of certain rock outcrops around the country led to his understanding of the immensity of geological time, most especially in the creation of unconformities. An unconformity is a geological feature where rocks of differing ages are found one above the other today, often with different angles of bedding (or layering). Hutton recognised that for an unconformity to form there must have been a large gap in time between the formation of the oldest rock and the youngest rock. Siccar Point in Berwickshire is perhaps his most famous unconformity, well known to geologists around the world.
He also demonstrated that igneous rocks were once molten. Through his study of Salisbury Crags, a Carboniferous igneous intrusion (sill) in Edinburgh, he demonstrated how the molten rock had forced its way between layers of sandstone before cooling to form rock. He published the results of his studies in his ‘Theory of the Earth’ in 1795.
R. L. Stevenson: “Hutton the geologist, in quakerish raiment, looking altogether trim and narrow, as if he cared more about fossils than young ladies.”
John Playfair: “His figure was slender, but indicated activity; […] His eye was penetrating and keen, but full of gentleness and benignity.”
“His conversation was inestimable; as great talents, the most perfect candour, and the utmost simplicity of character and manners, all united to stamp a value upon it. He had, indeed, that genuine simplicity, originating in the absence of all selfishness and vanity, by which a man loses sight of himself altogether, and neither conceals what is, not affects what is not…”
“A brighter tint of gaity and cheerfulness spread itself over every contenance when the Doctor entered the room…”
“With this exquisite relish for whatever is beautiful and sublime in science, we may easily conceive what pleasure he derived from his own geological speculations. […] to him they were matter, not of transient delight but of solid and permanent happiness.”