I did an OR search and came up with three hits for Earl about the time of your query.
The first is:
GENERAL ORDERS No. 51.
HDQRS. DEPT. OF THE GULF, 19TH A. C.,
Before Port Hudson, June 22, 1863.
I. Corpl. I. N. Earl, Company D, Fourth Wisconsin Volunteers, is hereby promoted to be first lieutenant of the same company and regiment, to date the 14th June, 1863, for gallant and meritorious conduct before Port Hudson, from the 1st to 14th June; for conspicuous gallantry in the assault upon the enemy's lines on the 14th, and for his subsequent zeal, daring, and good conduct. This appointment to be subject to the approval of the Governor of Wisconsin.
II. Col. S. G. Jerrard, Twenty-second Maine Volunteers, is hereby dishonorably dismissed the service of the United States, to take effect June 14, 1863, subject to the approval of the President,(*) for having, while temporarily in command of his brigade, when the column, of which his regiment formed a part, was ordered to take a portion of the enemy's works by assault, and when the column was at the foot of the parapet preparing for the assault, used discouraging and insubordinate language in the presence of a large number of officers and enlisted men, said language being in part to the purport that "rather than attempt to lead or put his command over that parapet, he would relinquish his command and go to the rear," or words to that effect; and, further, for using words to the same effect to a staff officer of Col. Joseph S. Morgan, Ninetieth New York Volunteers, commanding brigade, his superior officer, when ordered by the said Colonel Morgan, through the said staff officer, to assault the works. This order will be read to the delinquent in the presence of his regiment and of the brigade to which his regiment belongs.
III. This order will be read at the head of every regiment, battalion, and battery before Port Hudson, at retreat to-morrow.
By command of Major-General Banks:
RICH'D B. IRWIN,
Assistant Adjutant-General.
OR S1-V26-1, pp. 589/90
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See also pages 320 & 836
Good Hunting,
George Martin