A letter sent by Charles Darwin to marine biologist George Wallich in 1860 is up for auction at Nate D Sanders.
It dates to December 12, 1860 - a year after his ground-breaking work On the Origin of Species was published.
Wallich was the author of Notes On The Presence Of Animal Life At Vast Depths In The Sea, a study that clearly fascinated Darwin.
Darwin's letter reads in part: "I beg permission to thank you sincerely for sending me your 'Note on Animal Life at Vast Depths'.
"It has interested me extremely. You have indeed made a grand beginning at an admirable field of research…
"Is it not a most curious fact that the water at such profound depths and under such a vast pressure, should retain oxygen for the respiration of the animals mentioned by you.''
Bidding on the lot starts at $69,500 ahead of a close date of February 25.
A letter sent by Saint Junipero Serra in 1777 is offered with an opening bid of $50,000.
Serra was a Spanish missionary to California.
Serra asks the viceroy of New Spain (the name for the collective Spanish colonies in the Americas) for money to repair the San Diego mission following its destruction in a Native American uprising.
Serra was beatified by Pope John Paul II in 1988.
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