He explored the Two Rivers in the southern region and successfully mapped the area where the Marsh Arabs (Ma'dan) lived on islands built of reeds.
[7] He traveled south to the Pirate Coast (now the United Arab Emirates), then north all the way to Istanbul, before he floated his raft, with a goat for milk, twelve watermelons, a bag of rice, his cargo of soap and supplies, six hundred miles along the Euphrates to Al-Fallujah.
[8] In 1907–08, Van Ess acted as the official interpreter and local expert for a British survey led by William Willcocks to study the ancient irrigation systems.
To commemorate Van Ess's 25th anniversary, local Muslim, Christian and Jewish leaders donated $1,800 to build High Hope the first science lab in the Near East.
For example, Ephraim Avigdor Speiser, professor of comparative Semitic studies, assigned Van Ess's book at the University of Pennsylvania in the late 1920s.
[10] Agatha Christie referred to "getting on with Van Ess's spoken Arabic" in Come, Tell Me How You Live, her 1946 memoir about conducting research in Iraq with her husband, the archaeologist Max Mallowan.
"[13] He disagreed with (1) bringing a non-Iraqi king into power and (2) with the notion that the majority of Iraqis wanted independence or were ready for it.
Thus, he differed with the leading British specialists on Iraq, Col. T. E. Lawrence and Gertrude Bell, a close family friend.
"When Miss Bell and the other members of the Arab Bureau drew a line around Iraq and called it a political entity, they were flying in the face of four millenniums of history.