Heitman in "Historical Register and Dictionary of the U.S. Army" Vol. 1 does not list Daniels in his biographies. However, he does list him in Vol. 2, Part III, Sect. 4, p. 166 (Captains of Light Batteries or Light Artillery...)as you describe.
L. Van Loan Naisawald in "Grape and Canister, the Story of the Field Artillery of the Army of the Potomac, 1861-1865" does mention the 9th Michigan Battery, under the command of Captain J. J. Daniels at Gettysburg, supporting cavalry and armed with 3" rifles on p. 421. Referring to the third day of the battle, he says, "Daniels immediately ordered his men into their saddles and onto the limbers, and away he galloped to Newton's support. As they reached the position, the general waved them into line and yelled at Daniels to beat down the enemy fire." The author is referring to the Second Corps area around the copse of trees. In the notes he refers to OR, XXVII, 1, p.1021. In his tabulation of Gettysburg artillery strength, he says Daniels battery was in the 1st Brigade, Cavalry Corps.
Edwin B. Coddington, In "The Gettysburg Campaign, A study in Command", mentions Daniels in a note on p. 789.
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