They did it by pulling the thread off a reel, and stretching it alongside a one-fathom-long rod, and counting off fifty fathoms. One end of the thread Hooke tied to a heavy brass slug. He set the scale up on the platform that Daniel had improvised over the mouth of the well, and put the slug, along with its long bundle of thread, on the pan. He weighed the slug and thread carefully – a seemingly endless procedure disturbed over and over by light gusts of wind. To get a reliable measurement, they had to devote a couple of hours to setting up a canvas wind-screen. Then Hooke spent another half hour peering at the scale's needle through a magnifying lens while adding or subtracting bits of gold foil, no heavier than snowflakes. Every change caused the scale to teeter back and forth for several minutes before settling into a new position. Finally, Hooke called out a weight in pounds, ounces, grains, and fractions of grains, and Daniel noted it down. Then Hooke tied the free end of the thread to a little eye he had screwed to the bottom of the pan, and he and Daniel took turns lowering the weight into the well, letting it drop a few inches at a time – if it got to swinging, and scraped against the chalky sides of the hole, it would pick up a bit of extra weight, and ruin the experiment. When all three hundred feet had been let out, Hooke went for a stroll, because the weight was swinging a little bit, and its movements would disturb the scale. Finally it settled down enough that he could go back to work with his magnifying glass and his tweezers.