Purpose of Decanters?

A captain's decanters design lowers the center of gravity so that it is less likely to spill during rough seas. It has been romoured that alcohol can leach the leach lead out of some old lead crystal decanters. Some decanters meant for spirits can be very generous to angels due to their less than air tight stoppers.

A decanter also allows one to judge the color before the wine is in the glass.

Actually some people put marbles that have been steralized then brought down to room temperature into their decanters to raise the level of the liquid to force air out of the decanter to help preserve any unused wine. Care must be used in order not to spill the marbles into delicate stem ware. Besides the marbles are unpleasant when swallowed.