May and his troopers, alert for such an adventurous enterprize, stole onward towards Matamoros, under cover of night, and, about nine o'clock, beheld the enemy's camp fires on the field of Palo Alto. Avoiding the outposts and cautiously circling the Mexican front, he passed the foe, and galloped towards the American fort, until, hearing no sound of cannon in that direction, he halted with his command under the protecting screen of an extensive chapparal, about seven miles from Matamoros. Here he detached Walker and six of his rangers, best skilled in woodcraft, to communicate according to orders, with Major Brown, while he awaited their return in his concealed position. It was between two and three o'clock in the morning that Walker crept up to the bastions of our fort and was hailed by the sentinel. As soon as he was recognized his party was placed in a secure position, and the bold ranger admitted by a ladder to the fort. Major Brown reported the facts of the assault from Matamoros and the condition of his defences, as speedily as possible, and Walker and his men, mounting fresh horses, dashed off towards May so as to pass the enemy's lines before day-light. But, as he approached the thicket where he left the command, he found the troopers gone; and returning to the fort, which he reached before _reveille_, he awaited the approach of night before he again attempted to perform his dangerous service. Meanwhile May and his men had remained in their saddles until about half an hour before day, when, from the protracted absence of the ranger, they believed that the enemy's scouts had detected him. Walker had been already away about six hours; and as May's force was unable to cope with the supposed numbers of the Mexicans, and peremptory orders had been given to retire to Isabel, he immediately passed down the enemy's lines at a brisk gallop over the prairie. About twelve miles from our camp he suddenly discovered a hundred and fifty lancers drawn up across the road to dispute his passage, but speedily forming his line, he charged the troop, and, driving it towards the Mexican camp, followed the fugitives for three miles on his wearied horses. Fearing, however, that larger forces might be lying in ambush in the fields, and perceiving that the enemy's cavalry was fleeter than his own, he abandoned the pursuit and reached Point Isabel about nine o'clock.