G.H. Hill grandfather was a different Gabriel Holmes than the father of Theophilus. I have done a little geneological work on him, and have not found a tie, but I am certain that they were relatives. My surmise is that Hill ran for cover to the Ordnance Department after Holmes was sacked as the TM commanding general. Hills career had been attached to Holmes star, and as his personality was somewhat waspish, he probably would not have fit in well in a staff position under Kirby Smith.
A caveat about Albaugh's book. He transcribed less than half of Hill's letters, and it makes little rhyme or reason as to what he omitted. The letters in the three weeks prior to Mansfield really show the urgency of getting ammunition produced and to the field.
The letter book and the monthly account book have both been microfilmed by the NARA. The account book starts as the account book for the Little Rock Arsenal concluding in July 1863, and the next page starts with Tyler in October 1863 and runs through the end of the war. As it gives monthly production records, it really shows the development of supply in the west and the transition from early production of .69 caliber smoothbore ammunition in 1862 to almost entirely rifle ammuntion by 1864. These two books plus a fragmentary record of the Arkadelphia Works that we have here in Tyler are the only surviving records of the Ordnance Department in the TM.
Hill comes across as a very competent, outspoken, and by the book officer. He feuded and complained constantly with and of his superior in Shreveport, but it is the tidbits that come from his letters that show his personality and conditions in the west. In one instance he requested that he be allowed to buy red cloth that he had located so that his mens uniforms could have proper trim, and in another complained that the wood screws sent to him for ammunition boxes were only an inch and a half long, whereas the Ordnance Manual specified 1 3/4" screws.