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less severe is advancing, and will present itself within thirty or forty hours. When the form seems past, and the sky is clear, should a few fine cirrus clouds be seen brushed back at their E. extremities, the storm in all probability is really past and fair weather setting in [because the dry Polar current is asserting its supremacy overhead]; but if the cirrus continues to prevail in all directions, interlaced in the sky, a second storm is approaching.
If cirrus forms during fine weather with a falling barometer, a change is sure to occur.
Cirrus is especially associated with easterly winds.
A mass of cirrus with the fibres pointing upwards denote rain, but with the fibres downwards, dry though possibly windy weather. When cirrus lies from W. to E. a storm is imminent.
Cirro-cumulus ("mackerel sky") occurs frequently in summer in connection with dry summery weather. When enduring, cirro-cumuli clouds indicate a continuance of such weather and a rise in the barometer.
Cumulo-stratus immediately precedes the fall of rain or snow, according to the season of the year.
Cirro-stratus is especially a precursor of storms. Its greater or less abundance and permanence afford a clue to the probable nearness or remoteness of the storm that is impending.
Since it possesses great extent and evenness of texture with slight depth, it is the cloud in which halos and such optical atmospheric phenomena present themselves, and therefore
