In certain latitudes there comes a span of time approaching and following the summer solstice, some weeks in all, when the twilights turn long and blue. This period of the blue nights does not occur in subtropical California, where I lived for much of the time I will be talking about here and where the end of daylight is fast and lost in the blaze of the dropping sun, but it does occur in New York, where I now live. You notice it first as April ends and May begins, a change in the season, not exactly a warming—in fact not at all a warming—yet suddenly summer seems near, a possibility, even a promise. You pass a window, you walk to Central Park, you find yourself swimming in the color blue: the actual light is blue, and over the course of an hour or so this blue deepens, becomes more intense even as it darkens and fades, approximates finally the blue of the glass on a clear day at Chartres, or that of the Cerenkov radiation thrown off by the fuel rods in the pools of nuclear reactors. The French called this time of day “l’heure bleue.” To the English it was “the gloaming.” The very word “gloaming” reverberates, echoes— the gloaming, the glimmer, the glitter, the glisten, the glamour—carrying in its consonants the images of houses shuttering, gardens darkening, grass-lined rivers slipping through the shadows. During the blue nights you think the end of day will never come. As the blue nights draw to a close (and they will, and they do) you experience an actual chill, an apprehension of illness, at the moment you first notice: the blue light is going, the days are already shortening, the summer is gone. This book is called “Blue Nights” because at the time I began it I found my mind turning increasingly to illness, to the end of promise, the dwindling of the days, the inevitability of the fading, the dying of the brightness.

Blue nights are the opposite of the dying of the brightness, but they are also its warning.