On either flank of this enclosure, and twenty yards or so distant from it, paced a sentry.

Every two hours, as we have said, they were relieved, and in the alternate hours the posts were visited by the sergeant or corporal of the guard, who took turns in attending to this service.

The squad that came off duty in the morning was allowed during the day to take naps in the wagons, and was not put upon the harder camp labor, such as gathering firewood, going for water, etc.
The two ladies and the Indian women slept at night in the wagons, not only because the canvas tops protected them from wind and dew, but also because the wooden sides would shield them from arrows.

The men who were not on guard lay under the vehicles so as to form a cordon around the mules.
Thurstane and Coronado, the two chiefs of this armed migration, had their alternate nights of command, each when off duty sleeping in a special wagon known as "headquarters," but holding himself ready to rise at once in case of an alarm.
The cooking fires were built away from the park, and outside the beats of the sentries.

The object was twofold: first, to keep sparks from lighting on the wagon covers; second, to hide the sentries from prowling archers.
At night you can see everything between yourself and a fire, but nothing beyond it.