In the first six lines of the poem, Arnold creates a tone of calm, but yet there is an uneasiness to this apparent tone of tranquility, as the poet mentions, with a stylistic break in thought indicated by a long dash, that on the French coast "the light / Gleams and is gone...," using a device of antithesis to suggest a finality to the tonal peace of the moment.
There is a static, almost lifeless quality to the stylistic choice of brief three-word sentences arranged as clauses containing merely subject + linking verb + predicate adjective. Certainly, the clause "on the French coast the light / Gleams and is gone" creates a tone of finality. And, while in the sixth line the light/night device contradicts the death of light since the speaker calls his lover to the window in order to enjoy the sweetness of "the night-air," the use of the word night connotes a temporality to the night's sweetness because night will end with daylight.
In addition, the device depicting contrast of light and dark images with images of the moon and the passing of light from the French coast across from Dover Beach as well as the images of darkness of night outside the window suggests a temporal quality to any tone of peace that the speaker may feel.