With a silver lining

The cloudspotter’s guide
By Gavin Pretor-Pinney,
Sceptre, £ 8.15

The poet Shelley made the cloud say, ?I am the daughter of Earth and water,/ And the nursling of the Sky;/ I pass through the pores of the ocean and shores;/ I change, but I cannot die.?? Clouds are endlessly fascinating not only because they change shape and colour all the time but also because they bring together all the five elements. The presence of four of the elements are obvious in the making of clouds. When thunder and lightning occur, they introduce the fourth, fire.

Gavin Pretor-Pinney?s wonderful book engages with the fascination that clouds hold out for human beings. Shape, size, colour and the way that these can be read to predict the weather ? all these combine to make clouds a subject of observation and discussion. But even those who do not have a technical interest in clouds are drawn to them. It is for them that Pretor-Pinney has written this book.

It is difficult to think of somebody who has not looked at the sky and wondered about the clouds that occasionally fleet across it, or frown from it or decorate it like strands of cotton strewn against a blue background. Angry clouds can cut off sunlight and turn a bright day into dusk. The sun shining through clouds late in the afternoon can create a mellow and mysterious light. Bengalis say that this is the light to see a bride by.

Pretor-Pinney believes, ?nothing in nature rivals their [clouds?] variety and drama; nothing matches their sublime, ephemeral beauty.?? Yet, as he correctly notes, clouds are much maligned in common parlance. A cloud is always foreboding ? the contrast to sunshine which stands for clarity. ?A cloud on the horizon?? is a very common statement. This state of affairs, Pretor-Pinney believes, is unfair to clouds and is based on the fact that most people are ignorant of clouds, their character and what they mean.

This is a cloud lover?s book. But through his adoration of clouds, Pretor-Pinney shares with his readers a corpus of information and analysis which is educating and utterly captivating.

The various types of clouds ? Cumulus, Cumulonimbus, Stratus, Stratocumulus, Altocumulus, Altostratus, Nimbostratus, Cirrus, Cirrocumulus, and Cirrostratus ? are described in separate chapters.

The commonest of these clouds is Cumulus which typically form at 2000 to 3000 feet. They are randomly scattered across the sky and they look puffy; they develop vertically and convey the impression of a dome or a tower. These clouds stand in contrast to the Cirrus. They are high altitude clouds occurring at around 24,000 feet. They appear as delicate, white streaks; they are seldom thick. Cirrus clouds are responsible for the halo phenomenon around the moon. They can be harbingers of deterioration in the weather. Mountaineers high up on the Himalaya, especially above 26,000 feet, the death zone, watch the Cirrus clouds with great care.

In tropical climes, the cloud formation that attracts the most attention and dread is Cumulonimbus, the thunderstorm clouds. They can form at anything between 2000 and 45,000 feet. They are enormously high and have a propensity to show off through thunder and lightning.

Rupert Brooke in a flight of imagination wrote that the ?Dead die not?? but inhabit mid-heaven as clouds and ?watch the moon, and the still-raging seas, and men, coming and going on the earth.?? Clouds are the minarets of heaven.