It will be readily understood that when a large party of men and dogs starts out over the trackless ice to the polar sea, where there is no possibility of obtaining a single ounce of food on the way, after several days' marching, the provisions of one or more sledges will have been consumed by the men and dogs.

When this occurs, the drivers and dogs with those sledges should be sent back to the land at once.

_They are superfluous mouths which cannot be fed from the precious supply of provisions which are being dragged forward on the sledges._ Still further on, the food on one or two more sledges will have been consumed.

These sledges also, with their dogs and drivers, must be sent back, in order to ensure the furthest possible advance by the main party.

Later on, still other divisions must be sent back for the same reason.
But my supporting parties had another duty to perform, only a little less important than the one already noted; that was to keep the trail open for the rapid return of the main party.
The magnitude of this duty is clear.