The nineteenth century maps and sections of the three Geological Surveys of the British Isles were printed from hand-engraved copper, then steel plates and coloured by hand. Flat copies were used in the offices of prospecting and engineering companies and are usually in better condition and more suited for framing. For fieldwork, maps were frequently cut into smaller rectangles and mounted on linen, so that they folded easily and compactly to keep dry in pockets to prevent the colours running in rain. In this form the maps were also easier to keep on shelves. Some of the folded maps and sections have attractive covers or sleeves.
To express the different rock types and their distribution clearly and accurately required the use of many colours, and made exceptional demands on the printing technology of the nineteenth century. Therefore the black line work was coloured by hand with water colour and coloured inks. The colours adopted for the different geological formations are still the national standard today and have been widely adopted around the world. Geological faults and major mineral veins were shown by coloured inks.
The recognition of distinctive fossil types is a major factor in defining sedimentary rock formations; in many coastal areas the locations of fossils in cliff sections is labeled on early maps. In igneous rock areas, crystal structure, grain and colour of distinctive mineral associations help geologists to link up observations over large areas; on the large scale surveys and sections this information is often noted.
These maps and sections are a tribute to the powers of observation and deduction of Victorian geologists, who compiled and published this fundamentally correct interpretation of the complex and varied geology of the British Isles. The maps are also interesting historically as they show the landscape, towns and cities as they were in the early 1800s. The topographic survey date is usually much earlier than the date given for the geological survey. Often railways were inserted at a later date without other topographic revision. The date given in this catalogue is for the geological survey except where a later railway insert date is recorded.