Traveling with his wife Luise and daughter Gertrude, he took the opportunity to travel and to visit acquaintances, one of which was Eugene W. Hilgard, professor emeritus of agricultural chemistry at the University of California at Berkeley, who was also his wife's cousin.
Коссель путешествовал со своей женой Луизой и дочерью Гертрудой, посетил своих друзей, в том числе кузена своей жены Юджина Хилгарда (Eugene W. Hilgard), почетного профессора агрохимии в Калифорнийском университете в Беркли.