The young Pip, in Dickens's Great Expectations, nightly "fell among those artful thieves, the nine figures, who seemed every evening to do something new to disguise themselves and baffle recognition".
Let us not quibble about the fact that Dickens overlooked the zero; let us instead examine how these "artful thieves" are used in furtherance of meteorology.
At various time every day, messages are transmitted from weather stations, ships at sea, weather-buoys and other installations to forecasting offices all around the world. An example might read something like this: 090300 03953 41360 53110 10067 20023 49968 52017 69921 78011 83710 85820. They comprise a report of the weather at the time.
The numbers allow forecasters anywhere in the world to visualise the weather at that place. The first two groups of figures give the time and date and tell from where the report originated.
The remaining numbers give precise information about different aspects of the weather - the visibility, the kind of cloud, its height, and how much of each type of cloud there is, the temperature and humidity, the speed and direction of the wind - and so on.
The numerical code has the advantage of being independent of the spoken language of both sender and recipient, and of being concise and easily handled by computer. Most importantly, it is precise; each of the code-figures is defined exactly, avoiding any ambiguity that might arise from using common words with differing individual or cultural shades of meaning.
This information, when received, finds its way on to a weather chart in the form of a cluster of numbers and symbols arranged around a "station circle". The barometric pressure is plotted in the "north-east" corner of the cluster.
Just below it, immediately to the right of the station circle in the "east" position, is the pressure tendency, the amount by which the pressure has risen or fallen during the previous three hours.
Further down, plotted in red, is a symbol which signifies what the weather has been like for the six hours prior to the time of the report. A single dot indicates rain, a comma is used for drizzle, a triangle for showers, a star for snow, and other signs for any kind of weather.
And so it goes, right around the station circle. Temperature, humidity and wind, together with details of the cloud are all included in this compact ensemble of meteorological hieroglyphs. When the complete chart is plotted, it is possible for someone with a little practice to assimilate at a glance the weather pattern over a whole continent.