Caps. Lower-case. Greek name. English sound. [Greek: A] [Greek: a] Alpha. A. [Greek: B] [Greek: b] Beta. B. [Greek: G] [Greek: g] Gamma. G. [Greek: D] [Greek: d] Delta. D. [Greek: E] [Greek: e] Epsilon. E short. [Greek: Z] [Greek: z] Zeta. Z. [Greek: H] [Greek: h] Eta. E long. [Greek: Th] [Greek: th] Theta. Th. [Greek: I] [Greek: i] Iota. I. [Greek: K] [Greek: k] Kappa. K. [Greek: L] [Greek: l] Lambda. L. [Greek: M] [Greek: m] Mu. M. [Greek: N] [Greek: n] Nu. N. [Greek: X] [Greek: x] Xi. X. [Greek: O] [Greek: o] Omicron. O short. [Greek: P] [Greek: p] Pi. P. [Greek: R] [Greek: r] Rho. R. [Greek: S] [Greek: s] Sigma. S. [Greek: T] [Greek: t] Tau. T. [Greek: U] [Greek: u] Upsilon. U. [Greek: F] [Greek: f] Phi. F. [Greek: Ch] [Greek: ch] Chi. Ch. [Greek: Ps] [Greek: ps] Psi. Ps. [Greek: Om] [Greek: om] Omega. O long. _Roman numerals._ I 1 | IX 9 | LXX 70 | D 500 II 2 | X 10 | LXXX 80 | DC 600 III 3 | XIX 19 | XC 90 | DCC 700 IV 4 | XX 20 | C 100 | DCCC 800 V 5 | XXX 30 | CL 150 | CM 900 VI 6 | XL 40 | CC 200 | M 1000 VII 7 | L 50 | CCC 300 | MD 1500 VIII 8 | LX 60 | CD 400 | MCM 1900 Mathematical signs. + plus. ~ difference - minus. integration. × multiplied by. equivalence. ÷ divided by. : ratio. = equality. geometrical proportion. ± plus or minus. -: difference, excess. square. therefore. rectangle. because. triangle. infinity. circle. varies as. angle. radical. right angle. ° degree. or > greater than. ' minute. or < less than. " second. perpendicular. NAMES OF ROCKS. The following list was prepared in the geologic branch for the use of geologic draftsmen to enable them to select appropriate symbols for rocks that may be referred to in preliminary drawings by name only. For sedimentary rocks dots and circles, parallel lines, and broken or dotted lines are used; for metamorphic rocks short dashes arranged without definite patterns; and for igneous rocks patterns composed of short dashes, triangles, rhombs, crosses, and cross lines. All these patterns are shown in Plate III. _Sedimentary material._ [Including residual, detrital, eolian, glacial, organic, and chemically precipitated material.]