The grave is located along the outer wall of the cemetery. 

A small tomb with an inscribed oval stone on a sepulchral tomb.

George S. Hackley was a midshipman in the US Navy who fought in the Barbary wars assigned to Gunboat 2.  During the conflict, he died in Syracuse (Siracusa), Italy, possibly from battle wounds.  

From US Naval Records (Register of US Naval & Marine Corps Officer 1801-1807):

Hackley, George S.

Midshipman, January 3, 1801.

Served in U. S. S. Essex during Quasi-war with France; General Greene in ordinary at Washington Navy Yard, 1802-1803; Essex, John Adam ~ ,and Scourge in the Mediterranean, 1804-1805; Gunboat No. 2 preparing for a cruise in the Mediterranean April to July 1805.  Died July 8, 1805.

The text on the tomb is written in English and reads:

To the memory

 of

GEO. HACKLEY

Midshipman

Of the United States Navy

Of America

Died July 12, 1806

 Aged 26 years

Note:  The navy record indicates he died on July 8, 1806; inscription on the gravestone is very difficult to read.