When Admiral Sir Francis Beaufort devised his scale of wind strength in 1805, precise measuring instruments were unavailable. Although we now have alternatives, his methods of assessment are still applicable.

Gale force winds are now hitting every weather forecast we listen to, but how many of us would know a gale from a strong breeze, or know when gale force became storm force. Here is a guide to the points on Admiral Beaufort's scale.

0: Calm: smoke rises straight upwards.

1: Light air: not strong enough to blow weather vanes, but smoke curves. Aphids and spiders take to the air. Small ripples on the sea.

2: Light breeze: Leaves rustle, all flying insects take off.

3: Gentle breeze: Leaves and twigs move constantly. Too windy for spiders and aphids.

4: Moderate Breeze: Discarded paper blows down the street; small branches move. Mosquitoes stop biting.

5: Fresh breeze: Saplings sway. Flies are grounded - except horse flies.

6: Strong breeze: Large branches move; telephone lines whistle. Moths and bees stop flying. Large waves at sea.

7: Moderate gale: Whole trees move; butterflies stop flying.

8: Fresh gale: Twigs are blown off trees. Only dragonflies remain in the air. High waves at sea.

9: Strong gale: Roof repairers' phones become busy. All insects remain on the ground.

10: Whole gale: trees are uprooted; roof repairers might be able to fit you in the Tuesday after next.

11: Storm: Widespread severe damage. Air at sea white with driving spray.

12: Hurricane: winds at speeds over 75 mph.