Doctor Rush's eye water and the opening of the American west.

It has now been almost 200 years since Meriwether Lewis and William Clark set out from St. Louis on their successful western exploration in search of a practical overland and water route to the Pacific Ocean. Prior to their departure, Lewis traveled to Philadelphia to seek advice from the famous Dr. Benjamin Rush and others. Rush provided him with an elementary medical education, a liberal supply of his famous purgative pills, a chest of medical instruments, and a recipe for a lead acetate eye wash, together with the chemicals needed for its manufacture. In their journals, Lewis and Clark make frequent allusions to various eye afflictions suffered by their own troops and by the Native Americans encountered on their journey. Although herbal remedies were in common use, Rush's eye water proved very popular among the Native Americans for relief of their pain. It was so popular, in fact, that the explorers were able to make good use of it as diplomatic currency.