"I want to push right ahead." Push right ahead we did.

I continued quietly spurring my mule and then counseling the brute to take it easy.

Presently I noticed that the escort was stringing out far behind, as their horses became winded with the hard pace through the sand.

Custer, looking back, noticed the same thing.
"I think we are setting too fast a pace for them, Cody," he said, but when I replied that I thought this was merely the usual pace for my mule and that I supposed he was in a hurry he made no further comment.
Several times during the next forty miles we had to stop to wait for the escort to close up.

Their horses, sweating and panting, had reached almost the limit of their endurance.