Movement caught Jack's eye. He imagined for a moment that it was a watch-tower being knocked down by a sudden burst of French artillery. But when he looked, he saw he'd been fooled for the hundredth time. It was a windmill spinning. Then more movement out on the Ij: a tidal swell coming through and jostling the ships. A dredger full of hapless Hollandgänger moved up a canal, clawing up muck – muck that according to the Doctor would swallow and freeze things that had once been quick, and turn them to stone. No wonder they were so fastidious about dredging. Such an idea must be anathema to the Dutch, who worshipped motion above all. For whom the physical element of Earth was too resistant and inert, an annoyance to traders, an impediment to the fluid exchange of goods. In a place where all things were suffused with quicksilver, it was necessary to blur the transition from earth to water, making out of the whole Republic a gradual shading from one to the other as they neared the banks of the Ij, not entirely complete until they got past the sandbanks and reached the ocean at Texel.