Certain of the above flags are used singly with special significations, viz. A by H.M. ships on full speed trial, B to signify that explosives are being landed or discharged, C as affirmative, D as negative, P to denote that the ship is about to sail and S as signal for a pilot, while L is used in the United Kingdom to indicate infection from cholera, Yellow fever or plague, and Q is generally used aboard to denote liability to quarantine. Signals made with two flags are urgent and important. Of the three-flag signals those from ABC to AST relate to the compass; from ASU to AVJ to money; from AVK to BCN to weights and measures; BCO to BOZ to decimals and fractions; from BEA to CWT to auxiliary verbs and phrases; while the general vocabulary occupies the permutations from CXA to ZNV. The Code flag over two flags serves for Latitude and Longitude, Divisions of time, and the Barometer and Thermometer, and the Code flag under two flags from UA to ZY provides a numeral table. The geographical names of places are signalled by four flags from ABCD to BFAU, while the permutations from CBDF to CZYX are used for an alphabetical spelling table. This completes the flag signals of the Code, but it contains in addition a number of Distant Signals, Semaphore Signals and Morse Code Signals. Combinations from GQBC onwards are used for the names of ships, which will be found in separate publications. This new Code was published in 1899 and brought into force on 1st January, 1901, the old Code being used concurrently with it until the 31st December of that year. It has now reached the seventeenth edition, and a complete revision of it, which will probably entail the alteration of many of the flags, is occupying the attention of an International Commission, but it will be several years before this is brought into use. In making a signal, a ship first hoists her ensign with the code flag under it, and if necessary the distinguishing signal of the vessel or station with which she desires to communicate. On seeing this signal the ship (or station) addressed then hoists the "Answering Pendant" (i.e. the Code flag) at the "Dip," that is, some little distance below its position when hoisted "close up" to the block at the masthead or yardarm through which the signal halliards are rove. The first ship then hoists her own distinguishing signal, consisting of the four letters appropriated to her name, and then proceeds with the signal she wishes to make. When the first hoist is noted down and translated in the ship receiving the signal, this ship hauls the answering pendant "close up" to show that the signal is understood and keeps it there until the signalling ship has hauled that hoist down; the answering pendant is then again lowered to the "Dip" until the next hoist is disposed of, and when the ship signalling has finished, she hauls down her ensign to indicate that the message is at an end.