From Today in Science History:
Henry David Thoreau (Born 12 July 1817; died 6 May 1862). Thoreau, an American born in Concord, Mass., was an author, philosopher, poet and naturalist. He was a pacifist who always had Ralph Waldo Emerson around to bail him out of trouble. Thoreau was known as the “Hermit of Walden” because he lived in the woods around Walden pond for several years.As Henry got older, his attentions turned more towards the observing and recording of natural history in Concord. Henry kept thorough journals of natural history and the citizens of Concord regarded him as the town naturalist. Many scholars consider Henry David Thoreau to be the father of the American conservation movements.
Claude Bernard (Born 12 July 1813; died 10 Feb 1878). French physiologist (born near Villefranche) known chiefly for his discoveries concerning the role of the pancreas in digestion, the glycogenic function of the liver, and the regulation of the blood supply by the vasomotor nerves. On a broader stage, Bernard played a role in establishing the principles of experimentation in the life sciences. His Introduction to the Study of Experimental Medicine (1865) is a scientific classic.
Ynes Mexia (Died 12 July 1938; born 24 May 1870). Ynes Enriquetta Julietta Mexia was an American botanical collector, who developed her passion for botany and fieldwork in her 50′s, and yet was able to make about 150,000 collections in 12 years on seven expeditions. She was aged 55 when she made her first collecting trip. She accompanied Stanford’s Assistant Herbarium Curator, Roxanna Ferris, in Mexico. Her activity was remarkable, as she spent several years exploring for specimens in remote reaches of Central and South Americas. At age 59, she began a 2-1/2 year expedition in Peru and Brazil which included a three-month period trapped by floods with her team in a 600-m deep gorge which they escaped eventually by building a raft and running the river and its rapids.
David Douglas (Died 12 July 1834; born 25 Jun 1799). Scottish botanist who was one of the most successful of the great 19th century plant collectors. He established about 240 species of plants in Britain. His first foreign plant-hunting expedition (1824) was made throughout the Pacific Northwest of the U.S. The Douglas fir, which he cultivated from 1827, is named after him. He introduced other conifers including the Sitka spruce, now commercially important to the timber industry, and numerous garden plants and shrubs, including the lupin, California poppy and the flowering currant. At age 35, he died in by accident in Hawaii, when he fell into a pit dug by the islanders to trap wild cattle where he was trapped with a bull that also fell into the pit. He was gored to death by the bull.