The essay that was read to the continental army was the American Crisis
Explanation
The American Crisis book was written in the 18th century, and the author was Thomas Paine.
He was the most famous philosopher of the century.
He wrote several pamphlets during the revolution in America purposely to encourage the colonist in America to break from the British oppressors.
Once the declaration for war was made, his book was then read to the continental army.
The aim of reading the book was to boost morale as well as give the Americans a clear picture of what to expect.