Divisibility
Collier's New Encyclopedia (1921)
that general property of bodies by which their parts or component particles are capable of separation. Numerous examples of the division of matter, to a degree almost exceeding belief, may be easily instanced. Thus glass test-plates for microscopes have been ruled so fine as to have 225,000 spaces to the inch. Cotton yarn has been spun so fine that one pound of it extended upward of 1,000 miles, and a Manchester spinner is said to have attained such a marvelous fineness that one pound would extend 4,770 miles. One grain of gold has been beaten out to a surface of 52 square inches, and leaves have been made 367,500 of which would go to the inch of thickness. Iron has been reduced to wonderfully thin sheets. Fine tissue paper is about the 1,200th part of an inch in thickness, but sheets of iron have been rolled mu h thinner than this, and as fine as one 4,800th part of an inch 25-Vol. III-Cyc in thickness. Wires of platinum have been drawn out so fine as to be only the 30,000th part of an inch in diameter. Human hair varies in thickness from the 250th to the 600th part of an inch. The fiber of the coarsest wool is about the 500th part of an inch in diameter, and that of the finest only the 1,500th part. The silk line, as spun by the worm, is about the 5,000th part of an inch thick; but a spider's line is only the 30,000th part of an inch in diameter; insomuch that a single pound of this attenuated substance might be sufficient to encompass our globe. A single grain of the sulphate of copper, or blue vitriol, will communicate tint to five gallons ocatatertinentis case the sulphate must be attenuated at least 10,000,000 times. Odors are capable of a much wider diffusion. A single grain of musk has been known to perfume a large room for the space of 20 years.
What Has Changed in the Last Century
Collier's in 1921 treated divisibility as an open-ended property of matter, marvelling at gold leaf so thin that 367,500 sheets made an inch and at spider silk 1/30,000 of an inch across. Within a decade of that entry the atomic picture had hardened into fact — Jean Perrin's measurements of Brownian motion (1908-09) fixed the size of molecules, and Rutherford's 1911 nucleus and the electron showed that matter stops being divisible in the old sense and becomes structure: nuclei, then protons and neutrons, then quarks by the 1970s. The scanning tunnelling microscope (1981) let us photograph and even move single atoms, and graphene, isolated in 2004, is a sheet one atom thick — roughly 75 million to the inch, dwarfing the gold leaf that astonished the 1921 writer. The dilution and odour marvels at the end of the entry now have exact answers rather than wonder: a mole is a counted number of molecules, and detection limits are quoted in parts per trillion.
Written for this edition, 2026.