Interlocking
The boat continued moving forward for about a mile along the top of the wall. Long Tian didn't sit on the boat; he followed the boat, stepping on the top of the wall. At each predicted shallow trough location, he stopped and squatted down to examine it, scraping away the sediment with his fingertips to expose the bottom. The size and depth of the first few shallow troughs were the same as the first one. After confirming this, he stood up and continued forward, not lingering at each location for too long.
Upon reaching the seventh shallow groove, his fingertips encountered a different sensation than before—the bottom of the groove was about half a finger's width deeper than the previous ones, as if the design of this shallow groove was different from the previous ones. He squatted down and scraped away the sediment, revealing the complete shape of the groove bottom. The bottom of the groove was not smooth; it had a fine, dense pattern, like an engraved background, of uniform depth, arranged parallel to the direction of the groove, with width and spacing consistent with the serrations on the edge of the Dragon Bone Marker Disc. He ran his hand along the pattern on the bottom of the groove, and the aura of the Origin Return Pearl traveled along the pattern, flowing smoothly between the patterns without encountering much resistance.
He stood up and continued walking along the top of the wall for a while, stopping again at the eighth shallow trough. He scraped away the sediment to reveal the same pattern as the seventh. The ninth and tenth were the same. He straightened up and glanced at the top of the wall—the wall ahead still stretched straight, without bending or interruption at the end of his vision, unfolding continuously in the morning light.
Yu Jin jumped off the ship and quickly walked to his side, taking the dark gray bead from his hand and holding it in his palm, approaching the shallow groove with its underlying patterns. As the bead neared the edge of the groove, its surface lit up slightly, as if sensing some faint residual substance within the groove's patterns, maintaining a stable light-sensitive state as it approached. Long Tian crouched down, channeling the energy from the Origin Return Pearl back into the groove, tracing a circle along the patterns. As the energy flowed between the patterns, he felt a faint feedback, like an aftershock triggered by energy stored within the pattern structure, maintaining a stable intensity as it flowed. He withdrew his energy, stood up, took the dark gray bead from Yu Jin, and held it above the groove, maintaining a thin gap between the light layer on the bead's surface and the air layer at the bottom of the groove. As it hovered, the bead slowly sank slightly towards the bottom of the groove, guided by a continuous pulling force towards its center.
He steadied the bead and continued walking a few steps forward along the top of the wall. Upon reaching the next shallow trough, he repeated the same action—the bead, while suspended above the trough, sank again, as if guided by the same continuous pulling force in the same direction. Yu Jin, following behind, witnessed the bead's two sinking movements and spoke before Long Tian moved towards the third trough, his voice neither loud nor soft. "It's being pulled down. Each sinking is roughly the same magnitude and interval—it's as if there's some uniformly distributed force field at the bottom of the trough, pulling the bead down synchronously as it passes."
Long Tian crouched down in front of the third shallow trough, suspending the bead above it once more. This time, he didn't hold it steady, but instead slightly loosened his fingers, allowing the bead to sink naturally along the pulling force. It stopped about a finger's width from the bottom of the trough, hovering there, its surface glowing with a stable halo, the edge of which aligned with the serrations on the bottom of the trough. He withdrew his hand, watching the bead remain steadily suspended at that height above the shallow trough, without wobbling or shifting, as if supported by an invisible layer.
Yu Jin walked over and squatted down next to Long Tian. He observed the state of the bead for a while, then extended his palm upwards, hovering it about a hand's width below the bead. He sensed the energy characteristics transmitted from the bottom of the groove through the bead for a moment, then withdrew his hand. Long Tian extended his palm back towards the bead, letting it sink back into his palm along the original path. After withdrawing his hand, he stood up and handed the bead back to Yu Jin. Yu Jin took it and hung it back on his collar, adjusting the length of the drawstring so that it fit snugly against his collarbone.
Long Tian walked back to the side of the ship along the top of the wall, climbed onto the ship, squatted down at the hatch, and spread the silk map on the deck. He drew several short vertical lines on the section of the horizontal line at the top of the wall, corresponding to the shallow grooves with background patterns. After finishing the last stroke, he put the map away, stood up, and squatted at the bow for a while, looking at the wall that still stretched straight ahead. The wind and sunlight from the sea acted on the hull, maintaining its forward speed as it continued to move.