Below is a definition of Demonstration taken from Army Field Manual 1-02, 21 SEPT 2004. Although this is a modern definition, little change has taken place in the intent of the military operation.

A Demonstration in military lexicon is an action (NATO and DOD) 1. An attack or show of force on a front where a decision is not sought, made with the aim of deceiving the enemy. 2. (DOD only) In military deception, a show of force in an area where a decision is not sought; made to deceive an adversary. It is similar to a feint but no actual contact with the adversary is intended. (Army) 1. A form of attack designed to deceive the enemy as to the location or time of the decisive operation by a display of force. Forces conducting a demonstration do not seek contact with the enemy. (FM 3-0) 2. In stability operations and support operations, an operation by military forces in sight
of an actual or potential adversary to show military capabilities. (FM 3-07)

You can read both the Federal and Confederate reports of the demonstration in The War of the Rebellion: A Compilation of the Official Records of the Union and Confederate Armies. Washington, D. C.: U.S. Government Printing Office, 1880-1901, Series 1, Volume 53, beginning on page 417. There are thirty-nine total reports and Brigadier General Cumming's brief report (report # 34) is on page 482.

Below is a link on a brief description of the event.

http://www.nps.gov/history/hps/ABPP/BATTLES/ga006.htm

Respectfully,

Gerald D. Hodge, Jr.
M.A. Military History - Civil War Studies
War Between the States Historian
Historian: 39th Georgia Volunteer Infantry Regiment