For years was in the Netherlands a magazine published dealing with maritime affairs. It contained notes dealing with the Royal Dutch Navy and the Dutch merchant shipping/trade, but also supplied information dealing with foreign navies, especially of France and Great Britain . Occasionally we can find information dealing with the navies of other countries Russia , United States or even Mexico .
Since 1858 were in Russian harbours new pilot flags (C. de Reynold-system) obliged.
1. The Russian merchant flag put out from the top of the pilot signal-post, meaning that the pilot was coming to the arriving ship.
2.A black or other coloured ball flag put out from the top of the pilot signal-post, meaning that the pilot wasn’t able to come.
The arriving ship which wanted to enter the harbour and seeing these signals from the signal-post had to react with the signals obliged conform the regulations.
3. A red flag with the meaning that it was impossible to enter the harbour.
4. A blew flag with the meaning that ships which were lying in the road could best depart for sea due to (coming) heavy weather.
5. The same flag put out from the middle of the signal-post with the meaning storm was expected.
The signals which gave information dealing with the depth of the fairway, existed of balls or cones, put out from the end of the yards of the signal-post or from the signal-post self, lower of higher than the yards.
Source
G.A. Tindal en J. Swart. Verhandelingen en berigten betrekkelijk het zeewezen en de zeevaartkunde. Vol 5. Amsterdam, 1858, p. 457-458. Digitized by Google.