At the first outset, heavy, miry ground and a matted, marish vegetation greatly delayed our progress; but by little and little the hill began to steepen and become stony under foot, and the wood to change its character and to grow in a more open order.
There are no more uses of "open order" in the book.
Show samples from other sources
The noise of fourteen thousand aeroplanes advancing in open order.
Aldous Huxley -- Brave New World
With hounds questing ahead, in open order, the sons of Autolykos went down a glen, Odysseus in the lead, behind the dogs, pointing his long-shadowing spear.