From New Iberia Banks ordered Grover to send a detachment to destroy the famous Avery salt-works, on Petit Anse Island, distant about twelve miles toward the southwest. On the 17th of April, Grover accordingly dispatched Kimball on this errand, with his 12th Maine, the 41st Massachusetts, one company of the 24th Connecticut, and Snow's section of Nims's battery. The extremely rich natural deposit of rock salt was, at that time, in the hands of the Confederate government, being, indeed, the main source of supply of this indispensable article for the whole Confederacy, especially for the region between the Mississippi and the Atlantic. The works required for its extraction are, however, very simple, for the deposit lies close to the surface, and has only to be quarried in blocks of convenient size. These, always as clear and beautiful as crystal, have only to be crushed or broken to be ready to use for common purposes, and when pulverized, however rudely, yield the finest table salt. Kimball burned all the buildings, destroyed the engines and implements, with six hundred barrels of salt, and marched back to New Iberia, and, on the 19th, rejoined Grover on the Vermilion. The Confederates having drawn off the detachment and the guns previously posted to guard the works, Kimball met with no opposition. On the 17th of April, Grover, with the main body of his division, reinforced by Gooding's brigade, temporarily commanded by Colonel John W. Kimball, of the 53d Massachusetts, continued the pursuit toward Vermilion, while Banks, with Weitzel and Emory, marched to Saint Martinville, on the Teche. Early in the afternoon Grover caught sight of Green's rear-guard of Taylor's retreating forces, then about two miles distant, and in the act of crossing the Vermilion. Before Grover could overtake them, the bridges were in flames. Dwight's skirmishers deployed on the right and left of the road, and, with the help of the guns of Closson and Nims, drove off the enemy, posted to hinder or prevent the work of reconstruction. In this affair Dwight lost one killed and five wounded. The next day, the 18th of April, was spent by Grover in rebuilding the main bridge. Then began to be felt the need of such a force of mounted troops as on these plains formed the main strength of Taylor's little army, and the source of its safety; for Banks's cavalry, taken as a whole, with some splendid exceptions, was at this time greatly inferior, not only in numbers but in fitness for the work at hand, to the rough riders led by the restless and indomitable Green. A few more horsemen, under leaders like Barrett, Williamson, and Perkins, would have saved the bridge and insured the dispersion or the destruction of Taylor's force.