Anemometer, hygrometer and geared measuring instruments
Instruments to gauge wind speed, air moisture, sea miles and revolutions by geared wheels and a screw.
The sheet gathers small measuring instruments, each sketched beside a note of its purpose. One measures how far one travels per hour with the wind (an anemometer), needing a clock to show hours, points and minutes; another gauges the quality and thickness of the air and when rain is coming (a hygrometer); a third is meant to reckon miles at sea. A fourth device is a train of geared wheels whose revolutions multiply 1, 20, 200, 1000, driven through a lead or wooden screw filed to equal force, and it can also gauge the distance of thunder when clouds and treetops hang motionless.
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Geared revolution counter with a filed screw
A train of wheels multiplies turns so that the top vane makes 1000 turns for one turn of the first, in the steps 1, 20, 200, 1000. The screw is to be made first of lead or wood so that, by filing, it can be corrected to equal force. The first wheel's single turn is divided into 20 points by the second and 200 minutes by the third.
Anemometer for the speed of a wind
An instrument to measure how much distance is covered per hour by the course of a wind. Leonardo notes that a clock is required alongside it, one that shows the hours, points and minutes so the wind's run can be timed.
Hygrometer for air moisture and coming rain
A figure of a hygrometer, meant to know the qualities and thickness of the air and when it is about to rain. It reads the moisture of the atmosphere as a sign of approaching weather.
Instrument to reckon miles at sea
A figure of an instrument suited to knowing the miles travelled at sea. It stands among the other gauges as a navigator's measuring device.