1To Alexander Hamilton from Vincent Gray, [28 April 1804] (Hamilton Papers)
Baron Humboldt Supreme counseller of Mines in the service of His Prussian Majesty and Member of the Royal Academy of Science at Berlin, Travelling for the purpose of Advancing the progress of Natural History, being on his return from South America and New Spain, to the Dominions of his Prussian Majesty, by way of the United States, I take leave to recommend him to your particular friendship...