The difference in name of the same flag when carried on a ship would appear to indicate a difference in size appropriate to the different positions.
In the order in Council[172] directing what flags are to be used by diplomatic and consular officers, it is stated: "The flag to be used by Her Majesty's consular officers ashore to distinguish their residences is the Union flag."
There is, however, another official name of this flag given in official instructions which must be noticed.
The Military Regulations (1899) order to be displayed afloat, by generals and other military officers commanding stations, as their distinguishing flags, "the Union, bearing in the centre as a distinguishing mark the Royal Initials, surrounded by a garland on a blue shield and surmounted by a crown." For Commissioners and Consuls-general, "the Union, with the Royal Arms in the centre, on a white shield, surrounded by a green garland."
This same name "Union" is also given in directions respecting this flag when included as a part of a larger flag.
The Admiralty Instructions directing what Ensign is to be worn by all ships of the Royal Navy in commission state that they shall "bear a White Ensign with the Red St. George's cross, and the Union in the upper canton."
The Foreign Office Regulations direct that "consular officers when embarked in boats or other vessels shall use the Blue Ensign with the Royal Arms in the centre of the fly of the flag, that is, in the centre of that between the Union and the end of the flag."
Many other instances could be quoted, but these are typical and sufficient.
Three names are used—the "Union," "Union Flag," and "Union Jack," all describing the same flag.