siderites (σιδερίτης) 8, 11, 143.
siegelstein 11.
silk suspension for magnetick iron, 29, 30.
Silvaticus, Matthæus, 3.
silver, loadstone for, 109, 110.
similars, doctrine of attraction of, 50, 62.
Simon Stevinus, *v bis, 167, 168.
slate, magnetick properties of, 43.
smeargel (emery), 22.
Solinus, Caius Julius, 1, 9, 111.
Solomon the King, 4.
Sotacus, 9.
Stadius, 213.
stars are at various distances, 215.
steel, 23, 39, 69, 71, 93, 95, 147.
Stevinus, Simon, *v bis, 167, 168.
stomoma (στόμωμα) 23, 33, 36.
Strabo, 25.
succinum. See amber.
Sudini, or Sudavienses, 47.
sulphur, electrical by friction, 48, 53, 56, 59.
συνδρόμη, *vj.
συνεντελέχεια, 68.
Sussex, iron ore in, 22.
sympathy and antipathy, 65, 68, 112.
acitus, Cornelius, 25.
Taisner, or Taisnier, Joannes, 5, 107.
Tariassiona or Tarazona, 23.
terrella.
definition of, *vj, 12, 13.
poles and axis of, 13, 72, 81, 144.
divided into two parts, 72.
magnetick vigour, diagram of, 74, 75.
how small pieces of iron behave toward, 75, 76.
orbe of virtue of, 76, 77, 104.
"geography" of, 78.
æquinoctial circle of, 79, 144.
parallels of, 80, 211.
magnetick horizon of, 80.
proportion of the forces in, 81, 82.
experiment with iron sphere, 85.
small iron sphere and rod, 94, 102.
centre of magnetick virtue in, 95.
irregular terrella to exhibit variation, 155, 157.
to illustrate the dip of the needle, 190, 192.
analogy of, with the earth, 41, 78, 119, 211.
Thales of Miletus, 11, 61, 68, 208, 210.
theamedes, the, 18.
Thebitius, or Thebit ben Korrah, 117, 236.
Themistius, 71.
Theophrastus, 1, 9, 11.
Thomas Aquinas, 3, 64.
tides, the cause of, 86.
Tycho Brahe, 174, 229.
ariation of the compass, 7, 46, 79, 116, 151-163, 166, 167, 180.
variation at the Azores, 4, 154, 156, 167.
versorium, magnetick, definition of, *vj.
use of, 13, 115, 147.
versorium, non-magnetick, use of, 48, 49, 50.
verticity, 28, 115, 119-147.
acquired, 67, 68, 84, 85, 104, 123, 125, 129, 138, 139, 141, 142, 211.
in iron plates touched by loadstone, 84.
in iron sphere, 85.
how, in iron, 123, 139, 212.
in bracket in tower of St. Augustine's Church, Rimini, 141.
similar at ends of rod touched in middle, 84, 129.
by percussion, 139.
through interposed matter, 67.
not in bodies other than magnetick, 142.
æquator separates two kinds of, 79.
possessed by the earth, as a "Cause," 117.
change of, through change of mass, 72.
definition of, *vj.
described, 119, 120, 121.
destroyed by heat, 66, 93, 124.
earth produces it in loadstone and iron, 42, 140, 211, 212.
excited through greater distances in iron than in air, 104.
exists in all shapes of loadstone, 76.
helps the earth to keep its orbit, 224.
inhærent in wrought iron, 31, 115.
as a magnetick motion, 46.
mutation of, 120, 137.
magnitude of earth prevents variation of, 163, 164.
none acquired by iron rubbed on æquator of terrella, 148.
not affected by position of loadstone, 144.
of one loadstone as affected by another, 69, 138.
opposite, acquired by iron touched by loadstone, 115, 125, 129.
parts having same repel, 122, 133.
pole of, where last contact is, 149.
strengthened in versoria, 147-150.
strength of, decreases at once in both poles, 146.
vincentina, the, 48.
Vincent's Rock, gem of, 54.
eather affects electricks, 48, 53, 55, 56.
weighing the magnetick force, 108.
Wright, Edward, his prefatory address, *iij bis, 7.
wrought iron is magnetick, 29, 139.
outh preserved by loadstone, 32.
eilam, the king of, 32.
Zimiri, 11.
Zoroaster, 209.
