Massachusetts Mounted Infantry, had been attacked at The Park early this morning by a rebel force of 500. I immediately took three companies of cavalry and started for his relief. Having passed tow miles beyond Plaquemine I met a returning force of the Thirty-first Massachusetts who reported that the rebels had been driven across Grand River. I then returned with my companies to this place. Lieutenant Miles, of the engineer corps, accompanied all these expeditions, and with his knowledge of the country was of great assistance in carrying out the object of the expedition. He has bene so faithful in all of his duties that praise is a poor recompense for his valuable services. February 7, Lieutenant Miles, with a cavalry escort, proceeded toward Grand River and completed his survey. He has received all the assistance I could give him, both from cavalry and Infantry. the parties sent out in these expeditions have been instructed to seize all arms in the possession of persons without proper permits, which will be turned over in obedience to your orders. Every search and seizure has been made under the charge of a commissioned officer, with instructions to carefully and faithfully perform their duties. In the execution of your orders the country between Donaldsonville and Plaquemine has been cleared of the enemy and their haunts broken up. I would respectfully suggest that the easiest and most practicable mode of observing the general avenues of approach from the Grossetete country to the La Fourche, and checking the passage of the enemy, would be to establish a post at Bayou Goula, composed principally of cavalry. This post would be easily defended, and by care and watchfulness could warn and protect the La Fourche country. With reference to your instructions that no plunder or license be permitted the utmost care and vigilance has been exercised, and every effort has been made, on the part of both officers and men, to fully carry out the object of the expedition. Where either officers or men have failed in their duty, punishment has been speedy. If there are may of the enemy remaining we have been unable to discover them. We have been obliged to take some private property, but only in cases of extreme necessity, and orders wereoutset from these headquarters that no property [should be taken] without authority from the same. In the several scouts that have been made and in swimming bayous the men lost the larger portion of their rations, and I was compelled, in order to subsist my men, to take some beeves. One cow belonging to Mr. Sneed and six yearlings belonging to Mrs. Randolph comprises all taken under my orders for the use of my command. Owing to the scarcity of wood some six cords were taken from Colonel Butler's plantation, for which proper certificates have been given.

Very respectfully, your obedient servant,

W. SAYLES,

Colonel Third Rhode Island Cavalry, Commanding Expedition.

Captain FREDERIC SPEED,

Assistant Adjutant-General.

JANUARY 30-31, 1865. - Expedition from Thibodeaux to Lake Verret and Bayou Planton, La., with skirmish (30th) near Lake Verret.

REPORTS.

Numbers 1. - Brigadier General Robert A. Cameron, U. S. Army, commanding District of La Fourche.

Numbers 2. - Captain Thomas W. Sayles, Third Rhode Island Cavalry.

Numbers 3. - Captain John H. Alexander, First Louisiana Cavalry.