They couldn’t be more different, a catholic priest active in the early 1500s and a scientist, teacher, pharmacist in the mid-1700s. One is well-known, the other not. But what they had in common was a striking curiosity about the world around them. And that they shared their observations through their writings. The basic message would seem to be that unless you look you won’t see!
Olaus Magnus (1490-1557) led quite a varied life. Trained as a catholic priest he made his living in his earlier years traveling throughout Scandinavia selling letters of indulgence. And taking notes and making sketches of what he observed as he went along. He must have been a copious note keeper for look at what these led to: his Carta Marina, the first recognizable map of Scandinavia – as a long peninsula with Baltic waters from north to south separating it from Finland and Baltic countries. He sailed with the Hanseatic league throughout the Baltic. We can safely assume the mariners knew well the shape of the seas and coasts along which they sailed, but this was probably valuable professional information they kept to themselves, and in any event they weren’t mapmakers, or we would have known this. While he never sailed to the Faroes or Iceland he drew these in about the right place suggesting he must have worked closely with the skippers to share their knowledge of coastlines. He drew merchant ships, some (protestant?) being attacked by serpents, but what caught my oceanographic attention is that he drew eddies in the ocean roughly where the Faroe Current runs today! (See my blog-post January 31, 2024.)
The map reads almost like a child’s book with its sketches of life all across the lands: fishing, hunting, skiing in the mountains, skating on frozen waters. Since he wouldn’t convert when Sweden adopted the Lutheran Faith in the 1520s, his properties were eventually seized. He lived in Rome for the latter part of his life. His Carta Marina was published in Venice in 1539. It was a major contribution. He later published a book in Latin (A description of the Northern Peoples.)
in which he elaborates in considerable detail each of the activities sketched in the map. It was later translated into many European languages.
Nils Gissler (1715-1771) was academically trained, having earned a PhD in medicine at Uppsala University. He became a high school (gymnasium) teacher in logic, physics, and medicine, he became the town pharmacist and eventually also the provincial physician. He established a botanical garden including medicinal herbs. It is said that he wrote a book on meteorology, but no record of it exists. But this hints at his interest in natural phenomena.
He evidently had a barometer (I assume it was a mercury barometer). Being a keen observer, he noticed that when the air pressure went up, the water in the harbor went down! He wrote an article about this for the Royal Swedish Academy of Sciences in 1747. Gunnar Roden learned about it and asked me for help in translating it from Swedish. You will find it here: https://journals.ametsoc.org/view/journals/bams/80/4/1520-0477_1999_080_0675_escton_2_0_co_2.xml
This appears to be the first mention of what we today call the inverted barometer effect. We seagoing oceanographers needn’t worry about it but matters a lot to satellite altimetry. In the article he also speculates on the ancient beach ridges or berms around the island where he lived. He speculated that somehow sea level is dropping over time. A later study of his paper suggests that he came up with a roughly 1 m per century estimate – which is close to modern estimates for the region. It would be another century before the concept of glacial rebound was proposed.