The most tonally unified of all the mountain landscapes — a work in which blue dominates everything: the sky, the mountains, the mist, the shadows. The range of blues employed is extraordinary: deep sapphire in the upper sky, cerulean in the cloud masses, teal and peacock in the mountain slopes, pale powder blue in the atmospheric distance, almost-white where the mist catches the light. Against this blue world, small touches of warm color — a yellow cloud at upper center, brown ochre passages in the mountain's rock faces — feel precious and specific, like warmth held in a cold place.
The mountains themselves occupy most of the picture field, pressed up close with no middle distance — the composition is essentially foreground rock and sky, with only the thinnest strip of green at the very bottom edge suggesting the observer's ground. This compression creates a sense of immersion, of being inside the mountains rather than viewing them from a distance.
The mist and atmosphere in this work are handled with genuine mastery. The white passages between the blue mountain masses are not voids but active atmospheric presences — Sidney understood that mountain mist is not nothing but a substance with its own color and edge and behavior. The way the mist curls around the rock faces, the soft bleed of blue into white at the ridgelines — this is the work of an observant and technically accomplished landscape watercolorist.
At the lower edge, tiny dark marks — perhaps figures or perhaps trees at extreme distance — provide the scale that reveals how large these mountains are. Without them the composition could read as geology at any scale; with them it becomes landscape at human scale.