The following links may help you:
http://www.tsl.state.tx.us/arc/archmail.html
http://www.tsl.state.tx.us/arc/pensions/introcpi.html
http://mdah.state.ms.us/arrec/gen_research.php
http://mdah.state.ms.us/arrec/faq.php
The pension application would tell you which regiment he served.
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The following census may be the same Daniel Long.
Name: Daniel Long
Age in 1860: 51
Birth Year: abt 1809
Birthplace: Ireland
Home in 1860: Pontotoc, Mississippi
Gender: Male
Post Office: Palmetto
Household Members:
Name Age
Daniel Long 51
Catherine Long 40
Daniel Long 13
Margaret Long 12
Hannah Long 9
Source Citation: Year: 1860; Census Place: , Pontotoc, Mississippi; Roll M653_590; Page: 0; Image: 79.
Source Information:
Ancestry.com. 1860 United States Federal Census [database on-line]. Provo, UT, USA: Ancestry.com Operations Inc, 2004.
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