Constable's paradoxical rainbow

Why the artist John Constable allowed himself poetic licence when painting rainbows.

John Constable's powers of observation and thirst for meteorological knowledge enabled him to paint more realistic skies than any other English artist (see John Constable's Skies, University of Birmingham Press, 1999). Constable believed that “painting is a science, and should be pursued as an enquiry into the laws of nature. Why then may not landscape painting be considered as a branch of natural philosophy, of which pictures are but the experiments?” This Baconian view was certainly applied to the clouds and weather in his paintings, but, as we shall see, not to all of his rainbows.

Constable's paintings of rainbows are almost as well known as his paintings of clouds, but whereas clouds are present in some form almost every day in England, rainbows are seen much less frequently and are therefore more mysterious. Constable painted rainbows that were meteorologically accurate, but also used them for artistic effect in situations in which they could never occur in nature, such as in Salisbury Cathedral from the Meadows (1831) (see above). Although Constable knew that a rainbow cannot be seen once the Sun is higher in the sky than 42 degrees and that the Sun must be directly behind the observer of a rainbow, it plainly is not so in this view of the cathedral. This enigma is difficult to explain. Why should Constable be such a perfectionist about the weather in his paintings, his dutiful wind and clouds and harmonic daylight, and yet be content to introduce a meteorologically impossible rainbow?

Constable wrote to his friend John Fisher in 1821: “The sky is the source of light in nature – and governs everything … Their difficulty [clouds] in painting both as to composition and Execution is very great, because with all their brilliancy and consequence they ought not to come forward or be hardly thought about in a picture – any more than extreme distances are – But these remarks do not apply to phenomenon – or what the painters call accidental Effect of Sky because they always attract particularly.”

Thus the rainbow, and other optical effects such as crepuscular rays, were given a special exemption by Constable, and although a rainbow cannot ‘come forward’ in a picture, Constable makes it clear that if he introduces such an effect he wants it to be attractive and ‘thought about’.

If one looks at the shadow of the fence-post in the bottom left-hand corner of the picture, the geography and the illumination of the cathedral suggest that the Sun has reached an angle just north of west, which, in mid-August, would be between 6 and 7 p.m. At that time, the height of the Sun in the sky is about 15 degrees, which means the rainbow should have a height of about 27 degrees, significantly smaller than observed. The rainbow is not the bow the artist would see but one that would be seen from the meadow on the right. It is not in the plane of the picture but comes out of the picture at a shallow angle. The lighting suggests that the Sun is to the right of the picture and not, as it should be, behind the observer. It would appear that Constable was quite happy to use an amount of poetic licence for his “accidental Effect of Sky”.

Contrast Constable's London from Hampstead Heath with a Double Rainbow – painted a few months after Salisbury Cathedral from the Meadows was exhibited at the Royal Academy – which showed that he was fully aware of the colour reversal and the size of the secondary bow.

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Constable's Salisbury Cathedral from the Meadows (1831).