“Friday, 2nd. Continued to coast up the N. fork [of the Platte River]; the bottoms of the river were in many places completely covered with Glauber Salts, so much so that even handfuls could be taken up perfectly white.”
Glauber’s salt is a hydrous sodium sulfate mineral, also known as sal mirabilis (wonderful or miraculous salt.) It was formerly used as a laxative, much as Epsom salt (magnesium sulfate) was, until gentler methods came along. Now the mineral is mainly used in the manufacture of detergents, and in paper pulping.
“Saturday, 3rd. Left the N. fork; a distance of 12 miles took us to a spring of cool, though unpleasantly tasted water. The day was intensely warm, and road mountainous; killed four buffalo and two deer.”
“Sunday, 4th. Pursued our way over hills and dales, scorched with heat; came to a small copse of red willows, from which issued excellent springs of water. Three buffalo killed, distance travelled 22 miles.”
Neither Bidwell, Jimmy John, or Father De Smet make mention of any celebration of Independence Day on the 4th of July, although it could hardly have gone unremarked. Their focus was on the day-to-day difficulties of the journey: the rough terrain, the need to find food and water, and the imperative to press on.