One of these circles marked the temperature, graduated from the lowest to the highest degree ever known in that latitude.

Another indicated the direction of the wind, while the depth of colour in the circle itself, graduated in a manner carefully explained to me, but my notes of which are lost, showed the exact force of the atmospheric current.

The third served the purpose of a barometer.

A coloured band immediately below indicated by the variations of tint the character of the coming weather.

This band stretched right across the face; below it were figures indicating the day of the year.