Hyetographic or Rain Map of Europe, by A.K. Johnston, presents a detailed representation of the distribution and intensity of rainfall across Europe, with a specific focus on the British Isles. Published in 1857 by William Blackwood & Sons and engraved by W. & A.K. Johnston, this map utilizes varying shades to indicate different precipitation levels.
The 19th century was characterized by advancements in the study of meteorology and climatology. This map reflects the era's growing understanding of weather patterns and precipitation distribution. It introduces terms like "ischvetoses," lines indicating regions of equal annual rainfall, and "isotherombroses," which outline the distribution of summer rain. These elements serve to highlight the varying climatic regions of Europe.
Moreover, the map provides details on the number of rainy and snowy days within a year for different regions, complemented by figures indicating the specific amount of rainfall on those days. The direction of rain winds is also marked, offering insights into prevailing atmospheric patterns.
Constructed on a scale set to French inches, the map offers a conversion guide for those familiar with English measurements. By adding one-fifteenth to any given figure on the map, one can determine its approximate value in English inches.
In its entirety, this map reflects the methodical approach of 19th-century cartographers, as they employed emerging knowledge to depict the climatic nuances of Europe with clarity and precision.