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LaTeX source for Symmetry Slides\documentclass{article} \usepackage{amsmath} \usepackage{amssymb} \begin{document} \setlength{\parindent}{0pt} \begin{center} {\LARGE\textbf{GEOMETRIC SYMMETRY}} \\ \ \\ {\Large\textbf{SLIDES}} \\ \bigskip\bigskip\bigskip ORDER FOR FRIEZE GROUPS \medskip \begin{tabular}{ll} t & L\\ tg & L$\Gamma$\\ tm & V\\ mt & C\\ t2 & N\\ t2mg & V$\Lambda$\\ t2mm & H \end{tabular} \end{center} \begin{center} ORDER FOR WALLPAPER GROUPS \\ \medskip \begin{tabular}{lllll} p1 & p2 & pm & pg & cm \\ pmm & pmg & pgg & cmm \\ p4 & p4m & p4g \\ p3 & p3m1 & p31m \\ p6 & p6m \end{tabular} \end{center} \newpage \begin{center} GEOMETRIC SYMMETRY---SLIDES \end{center} 010 (Cypriot Vase with the Name of Thales). \bigskip 020 SONNET ABOUT THE RAIN - Dobrivoje Jevti , 1978. B. Pavlovi , ``On symmetry and asymmetry in literature'', \textit{Comp.\ and Math.\ with Applics.}\ \textbf{12B} (1/2) (1986), 197--227, at p.208 = Istvan Hargittai, \textit{Symmetry Unifying Human Understanding}, Pergamon 1986, 197--227, at p.208. \bigskip 030 Hedgehog Edward Rolland McLachlan, \textit{The Cartoons of McLachlan}, Private Eye 1973. \bigskip 040 Palindrome. THE END - Frederic Brown. Martin Gardner, \textit{The Ambidextrous Universe}, Penguin 1970, end of Chapter 5 (pp.50--51). \bigskip 050 Palindrome BLACK AND WHITE by J.A. Lindon. \medskip Lived as a dog - o no! God, as a devil \quad Doom lives ever, it's astir, Eve's evil mood, Live, O devil, revel ever, live, do evil! \quad Do, O God, no evil deed, live on, do good! \medskip Howard W. Bergerson, \textit{Palindromes and Anagrams}, Dover 1973, p.117. \bigskip 060 m The human anatomy according to ideal principles. Venice, Academy. [N.B. Leonardo's notebooks were written backwards, from right to left]. Bruno Santi, \textit{Leonardo}, Constable 1978, p.41. \bigskip 070 m Mixtec culture: a sacrificial obsidian knife with mosaic handle. A two-handled mosaic serpent (below). These objects are believed to have been among the treasure presented to Cort\'es by Moctezuma. Hammond Innes, \textit{The Conquistadors}, Collins 1969, repr.\ by Fontana 1972, p.110. \bigskip 080 m (Russian imperial eagle). Alexander Pushkin, \textit{Boris Godunov} (Illustrated by Boris Zvorykin) (Introduction by Peter Ustinov), Allen Lane 1982, Back endpaper. \bigskip 090 m Flags of Europe I: 1, Denmark; 2, Norway; 3, Iceland; 4, Sweden; 5, Finland; 6, Greece; 7, Czechoslovakia; 8, Poland. Numbers 1, 2, 3, 4 (and 5 apart from the badge) have symmetry m but number 7 needs inversion of red and yellow to go with the mirror operation. G.\ Campbell and T.O.\ Evans, \textit{The Book of Flags}, Oxford University Press 1950, Plate XI. \bigskip 100 2 Fig.\ 129. M83. This picture of a face-on spiral galaxy was made of Kodak Vericolor II negative film, rather than by the three-colour superposition technique and shows much less intense but similar colours to the picture of NGC 2997 [Fig.\ 128 in the same book]. David Malin and Paul Murdin, \textit{Colours of the Stars}, Cambridge University Press 1984, Fig.\ 129. \bigskip 110 2m Fig.\ 133. Centaurus A. Basically an elliptical galaxy with a population of yellowish stars, Cen A is crossed by a band of dust which reddens the stars still further. Formed from the dusty material, blue stars and pink H II regions can be perceived along the rim of the dust band. David Malin and Paul Murdin, \textit{Colours of the Stars}, Cambridge University Press 1984, Fig.\ 133. \bigskip 120 2 (colour !) Back cover and p.13. The yin-yang symbol [tai-ji] surrounded by the eight trigrams. This arrangement is known as the Sequence of Earlier Heaven, or the Primal Arrangement (Roland Michaud). Neil Powell, \textit{The Book of Changes: How to Understand and Use the I Ching}, Orbis 1979 reprinted by Macdonald \& Co.\ under the Black Cat imprint. \bigskip 130 2 (colour !) Figure 6.8 portrays two ancient symbols belonging to the same group, the runic symbol for death and the well-known Chinese yin-yang symbol of universal duality. P.S.\ Stevens, \textit{Handbook of Regular Patterns}, MIT Press 1974, p.43, Figs.\ 6.8a and 6.8b. \bigskip 140 2 m, 3m, 4m, (near bottom centre), 14m (top), 31m (or thereabouts) An arrangement of diatoms from the South Pacific, photographed in polarized $\text{light}\times150$. Eric Linklater, \textit{The Voyage of the Challenger}, John Murray 1972 and Sphere 1974, p.228. \bigskip 150 4 Fig.\ 20 \textit{Aurelia insulinda}. Example of an organism possessing a four-fold symmetry axis (Haeckel). A.V. Shubnikov and V.A. Koptsik, \textit{Symmetry in Science and Art}, Plenum 1974, Fig.\ 20, p.20. \bigskip 160 4 8. A sprig of Codlins and Cream (Epilobium hirsutum) The whole plant grows to five or six feet Iolo A. Williams, \textit{Flowers of Marsh and Stream}, Penguin 1946 (King Penguin No. 27), Plate 8. \bigskip 170 Fig.\ 1. The starfish Pentaceraster mamillatus, one of the most conspicuous inhabitants of deeper sand bottoms, is 20 to 25cm across and bright red or orange in colour. This individual was brought up from the bottom at 15m and photographed on the beach . [Jana Island]. Philip W.\ Basson, John E.\ Burchard, Jr., John T.\ Hardy, and Andrew R.G.\ Price (illustrated and designed by Lisa Bobrowski), \textit{Biotopes of the Western Arabian Gulf}, Aramco (Dharan, Saudi Arabia) 1977, Fig.\ 1. \bigskip 180 6m W.A.\ Bentley and W.J.\ Humphreys, \textit{Snow Crystals}, McGraw-Hill 1931 and Dover 1962. \bigskip 190 2m, 3m, 6m W.A.\ Bentley and W.J.\ Humphreys, \textit{Snow Crystals}, McGraw-Hill 1931 and Dover 1962. \bigskip 200 7m and 5m (top left) \textit{Antedon bifida} (top right) \textit{Luida ciliaris} (always has 7 flattened rays) (centre left) \textit{Astropecten aranciacus} (centre right) \textit{Astropecton irregularis} (bottom left) \textit{Ceramaster placenta} (bottom right) \textit{Porania pulvillas} A.C. Campbell (illustrated by James Nicholls), \textit{The Seashore and Shallow Seas of Britain and Europe}, Collins 1976, p.241. \bigskip 210 8m, 9m, 12m and 5m (top left) \textit{Crossaster papposus} (8-13 blunt rays) (12 shown) (top right) \textit{Solaster endeca} (7-13 rays) (9 shown) (centre left) \textit{Marthasterias glacialis} (centre right) \textit{Asteriasw rubens} (bottom left) \textit{Stichastrella rosea} (bottom right) \textit{Coscinasterias tenuispina} (6--10 rays often of very different lengths) (8 shown) A.C.\ Campbell (illustrated by James Nicholls), \textit{The Seashore and Shallow Seas of Britain and Europe}, Collins 1946, p.\ 245. \bigskip 220 12 9. \textit{Sea anemone} (\textit{Halcampa chrysanthellum}). [It] is very much enlarged and inhabits sandy and muddy places, burying its worm-like body and extending its tentacles at its surface. T.A.\ Stephenson, \textit{Seashore life and pattern}, Penguin 1944 (King Penguin No. 15), Plate 9. \bigskip 230 20m (approx.) Floating sea slug attacking a jellyfish, Great Barrier Reef. David Attenborough, \textit{Life on Earth}, Collins/British Broadcasting Corporation 1979. \bigskip 240 Fig.\ 14--6 Asante brass weights in geometric shapes, used for measuring gold dust currency. Many of the designs have symbolic meaning; for example, a zigzag line represents the fire of the sun. British Museum. C. Zaslavsky, \textit{Africa Counts}, Prindle Weber and Schmidt 1973, p.176. \bigskip 250 The Seven Friezes \medskip \begin{tabular}{lllllll} L & L & L & L & L & L & L \\ L & $\Gamma$ & L & $\Gamma$ & L & $\Gamma$ & L \\ V & V & V & V & V & V & V \\ C & C & C & C & C & C & C \\ N & N & N & N & N & N & N \\ V & $\Lambda$ & V & $\Lambda$ & V & $\Lambda$ & V \\ H & H & H & H & H & H & H \end{tabular} \bigskip 260 Plate XV, Greek No. 1 Owen Jones, \textit{The Grammar of Ornament}, John Day 1856 and Van Nostrand Reinhold 1982. \bigskip 270 Plate VI. Egyptian No. 3 Owen Jones, \textit{The Grammar of Ornament}, John Day 1856 and Van Nostrand Reinhold 1982. \bigskip 280 Plate XCIII Leaves from Nature No. 3 Owen Jones, \textit{The Grammar of Ornament}, John Day 1856 and Van Nostrand Reinhold 1982. \bigskip 285 Granada. Sala de Reposo [del Ba¤o] [Baths. The Rest Hall or Hall of Repose in the Comares Palace Bath] (Postcard) \bigskip 290 p1 Plate X, No. 11. Ornament on the walls, Hall of the Abencerrages. Albert F. Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906. \bigskip 300 p2 24.9a Peruvian textile design 24.9b Peruvian textile design 24.9c Peruvian textile design P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984. \bigskip 310 pm (diamonds); cm (lozenges) Plate 31 Plate 32 Victoria and Albert Colour Books. \textit{Decorative Endpapers}, Webb and Bower 1985. \bigskip 320 pg M.C.\ Escher, Study for the lithograph ``Encounter'', pencil and ink 1944. Note that in this case it is impossible to bring, e.g., the two white men to coincidence by a rotation. Caroline H.\ McGillavry, \textit{Symmetry Aspects of M.C.\ Escher's Periodic Drawings}, International Union of Crystallography, Plate 3 = J.L.\ Locher, \textit{The World of M.C.\ Escher}, Harry N. Abrams 1971, Fig.\ 123. \bigskip 330 pg Plate 9 Plate 10 Victoria and Albert Colour Books. \textit{Decorative Endpapers}, Webb and Bower 1985. \bigskip 340 cm Plate V, No.\ 5. Ornament on the side of windows, Hall of the Two Sisters. Albert F.\ Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906. \bigskip 350 cm Plate IV, No. 4. Ornament at the entrance to the Ventana, Hall of the Two Sisters. Albert F.\ Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906. \bigskip 360 cm Plate XI, No.\ 12. Ornament in panels on the walls, Court of the Mosque. Albert F.\ Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906. \bigskip 370 p2mm Figure 27.4 (a) (top right) American Indian, Nez Perc\'e (b) (bottom left) Romanesque (c) (bottom right) mosaic pavement, Florence baptistry P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984. \bigskip 380 p2mg Chinese lattice designs 25.7 (a) (top) (Dye N2b, p.215) \phantom{25.7} (b) (bottom left) (Dye I3b, p.157) \phantom{25.7} (c) (top right) (Dye 7, p.307) P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984. \bigskip 390 p2gg 26.6 (a) Congo, Africa 26.6 (b) Italy, sixteenth century P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984. \bigskip 400 c2mm 28.4 (a) (top) Japanese 28.4 (b) (bottom left) Italian, sixteenth century 28.4 (c) (bottom right) medieval design P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984. \bigskip 410 p4 This pattern presents a tricky problem. It is formed by an array of starfishes, clams and snail shells. At first sight, one would mark as cell corners the points where four clams and four starfish meet. However, on closer inspection it is seen that the edges of this square are not true translations of the patterns; the snail shells halfway between these pseudocell corners are not repeated in identical orientation by such shifts\dots. On the other hand, the mid-point of the psueudo-cell, where four starfishes and four snail shells meet, is indeed a true fourfold rotation point\dots. Caroline H.\ MacGillavry, \textit{Symmetry Aspects of M.C.\ Escher's Periodic Drawings}, International Union of Crystallography 1965, Plate 13. \bigskip 420 p4mm Octagon allovers, Buddhist temples, Mount Omei, Szechuan 1800-1900 a.d. Fig.\ H 10a (top right) Fig.\ H 10b (top right) Fig.\ H 10c (bottom right) Fig.\ H 10d (bottom right) Daniel Sheets Dye, \textit{Chinese Lattice Designs}, Harvard University Press 1937 and Dover 1974, p.149. \bigskip 430 p4mm 34.6 (a) (top) Byzantine design 34.6 (b) (bottom left) tartan motif 34.6 (c) (bottom right) Mayan motif, Uxmal, Yucatan P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984, p.308. \bigskip 440 p4g M.C.\ Escher, Study of Regular Division of the Plane with Angels and Devils, Pencil, india ink, blue crayon and white gouache 1941. Plate 6. The pattern has evidently fourfold rotation and mirror-symmetry\dots. It is seen that near the bottom of the picture there is a row of three fourfold rotation points. Of these, only the first and third are equivalent by translation; the surroundings of the three points are alternatively `left' and `right' since there are mirror lines running between them. Choose the point in the middle of this row and find in the pattern three other fourfold points in the same orientation. These outline a square unit cell which is tilted at 45ø to the borders of the picture. Caroline H.\ MacGillavry, \textit{Symmetry Aspects of M.C.\ Escher's Periodic Drawings}, International Union of Crystallography 1965, Plate 6. \bigskip 450 p4gm 33.6a (top) mother-of-pearl inlay motif, Turkey 33.6b (bottom left) Arabian 33.6c (bottom right) Arabian P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984, p.298. \bigskip 460 p3 Plate XLVIII No.\ 58. Mosaic from the portico of the Generalife. Albert F. Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906. \bigskip 465 p3 Postcard with caption ``La Alhambra (Granada) Estucado''. \bigskip 470 p3m1 30.3 (b) (top left) Persian 30.3 (c) (bottom right) Chinese (Dye C12b, p.79) P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984, p.267. \bigskip 480 p31m 31.4 (a) (top left) Chinese 31.4 (b) (top right) Chinese (Dye C5a, p.72) 31.4 (c) (bottom) Russian P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984, p.275. \bigskip 490 12m or 4m (top); p6 (bottom) Plate XLII , Moresque No. 4 (Do not confuse with Plate XLII*, Moresque No. 4*) No.\ 6 (top) $\cong$ Albert F.\ Calvert, \textit{The Alhambra}, John Lane, The Bodley Head 1906, Plate LXXVIII, No.\ 106, Part of the Portico of the Court of the Fish Pond. No.\ 5 (bottom) $\cong$ Calvert, \textit{op.\ cit.}, Plate LXXX, No. 108, Ornaments on the walls, House of Sanchez. Owen Jones, \textit{The Grammar of Ornament}, John Day 1856 and Van Nostrand Reinhold 1982. \bigskip 500 p6mm 36.6 (a) (left) An ancient design from the palace at Nimrud, Mesopotamia 36.6 (b) (right) A Japanese design P.S.\ Stevens, \textit{Handbook of Regular Patterns}, M.I.T.\ Press 1984, p.328. 510 \bigskip p6mm 44. Some of the myriads of elegant basalt columns that make up the Giant's Causeway in Antrim, Northern Ireland. Most, but not all, are hexagonal. (Institute of Geological Sciences photograph). Peter Francis, \textit{Volcanoes}, Penguin 1976, p.220. \bigskip 520 p6mm Plate 10 B. Polygonal jointing in Tholeiitic Basalt lava. Giant's Causeway. H.E.\ Wilson, \textit{Regional Geology of Northern Ireland}, H.M.S.O.\ 1972. \bigskip 530 p6mm Plate 52. Workers of the dwarf honey bee gnawing wax off an abandoned comb and putting it into their leg baskets (see p.95). Karl von Frisch (with the collaboration of Otto von Frisch), \textit{Animal Architecture} (translated by Lisbeth Gombrich), Hutchinson 1975, p.97. \bigskip 540 p6mm Plate 49 (top left) Comb built by bees whose antennal tips had been amputated. The cells are irregular; their walls are excessively thick in some places, excessively thin in others, and there are holes. (See p.92). Plate 50 (top right) Bee with baskets filled with pollen. (See p.83). Plate 51 (centre) Bee with baskets filled with propolis. (See p.94). Plate 52 (bottom) Workers of the dwarf honey bee gnawing wax off an abandoned comb and putting it into their leg baskets. (See p.95). Karl von Frisch (with the collaboration of Otto von Frisch), \textit{Animal Architecture} (translated by Lisbeth Gombrich), Hutchinson 1975, p.97. \bigskip 550 pg$'$ (black and white) Fig.\ 137 (above) M.C. Escher, Study of Regular Division of the Plane with Horsemen, Indian Ink and Watercolour 1946 ( Magic Mirror, Fig.\ 225) Fig.\ 138 (below), M.C. Escher, Horsemen, Woodcut in three colours 1946 ($\cong$ \textit{Magic Mirror}, Fig.\ 224 $\cong$ \textit{Graphic Work}, Fig.\ 6) J.L.\ Locher (ed.), \textit{The World of M.C.\ Escher}, Harry N.\ Abrams 1971. \bigskip 560 Colour plane symmetry This is a more typical case of colour symmetry. The pattern is composed of fishes in four different colours and orientations. All the fishes of one colour have the same orientation and surroundings, so there is one fish of each colour per cell\dots. [Discussed also by Arthur L.\ Loeb, \textit{Color and Symmetry}, Wiley 1971, Chap.\ 22, pp.162--165] Caroline H.\ MacGillavry, \textit{Symmetry Aspects of M.C. Escher's Periodic Drawings}, International Union of Crystallography 1965, Plate 37. \bigskip 570 M.C.\ Escher, \textit{The Graphic Work of M.C.\ Escher}, Oldbourne 1961, Fig.\ 20 Bruno Ernst, \textit{The Magic Mirror of M.C.\ Escher}, Ballantine 1976, Fig.\ 244 J.L.\ Locher (ed.), \textit{The World of M.C. Escher}, Harry N.\ Abrams 1971, Colour Plate VII and Fig.\ 239 \bigskip 580 Tilings (Frontispiece) Johannes Kepler (1580-1630) is well known for his pioneering work in astronomy. He also made fundamental contributions to the theory of tilings, and some of his ideas have still not been fully investigated. We reproduce here tilings from his book \textit{Harmonica Mundi} (volume 2) published in 1619. The tiling marked Aa can be extended over the whole plane as shown in Figure 2.0.1 and described in Section 2.5. Branko Gr\"unbaum and G.C.\ Shephard, \textit{Tilings and Pattern}s, Freeman 1987. \bigskip 590 Tilings Figure 8.0.1. An attractive and ingenious pattern of squares from Islamic art (Bourgoin [1879, Plate 13]) perfectly coloured in four colours. The pattern is of type PP48A and it can be perfectly $k$-coloured if $k$ has one of the values $3n$, $6n$, $n^2$, $2n^2$, $3n^2$ or $6n^2$ for a positive integer $n$ (see Senechal [1979a]). Branko Gr\"unbaum and G.C.\ Shephard, \textit{Tilings and Pattern}s, Freeman 1987. \bigskip 600 Regular solids M.C.\ Escher, Study for the wood engraving "Stars", Woodcut 1948. J.L.\ Locher (ed.), \textit{The World of M.C.\ Escher}, Harry N. Abrams 1971, Fig.\ 151. \bigskip 610 Regular solids M.C.\ Escher, Stars, Wood engraving 1948. M.C.\ Escher, \textit{The Graphic Work of M.C.\ Escher}, Oldbourne 1961, Fig.\ 51 Bruno Ernst, \textit{The Magic Mirror of M.C.\ Escher}, Ballantine 1976, Fig.\ 209 J.L.\ Locher (ed.), \textit{The World of M.C.\ Escher}, Harry N.\ Abrams 1971, Fig.\ 152 \bigskip 620 Regular solids A.\ Holden, \textit{Shapes, Space and Symmetry}, Columbia University Press 1971, Plate opposite p.1. \bigskip 630 Fig.\ 26. Skeletons of various radiolaria (after Haeckel). BUT see H.S.M. Coxeter, Review of ``Symmetry'' by H. Weyl, \textit{American Mathematical Monthly}, \textbf{60} (1953), 136--139. A.F. Wells, \textit{The Third Dimension in Chemistry}, Oxford: Clarendon Press 1956. \bigskip 640 Regular solids Fig.\ 46. Here (Fig.\ 46) is his [Kepler's] construction, by which he believed he had penetrated deeply into the secrets of the Creator. The six spheres correspond to the six planets, Saturn, Jupiter, Mars, Earth, Venus, Mercurius, separated in this order by cube, tetrahedron, octahedron, dodecahedron, icosahedron. H.\ Weyl, \textit{Symmetry}, Princeton University Press 1952. \bigskip 650 Table 9. The thirteen semi-regular (Archimedean) polyhedra and their duals (a) truncated octahedron (b) truncated icosahedron (c) great rhombicuboctahedron or truncated cuboctahedron (d) snub cube (e) truncated tetrahedron (f) cuboctahedron (g) icosidodecahedon (h) small rhombidodecahedron (i) small rhombicosidodecahedron (j) truncated cube (k) truncated dodecahedron (l) truncated dodecahedron (m) snub dodecahedron. Open University Technology/Mathematics Course TM 361, \textit{Graphs, Networks and Designs}, TM 361--13 Geometry, p.36. \bigskip 660 Table 10. Some examples of space filling systems. Open University Technology/Mathematics Course TM 361, \textit{Graphs, Networks and Designs}, TM 361--13 Geometry, p.46. \bigskip 670 Crystal Fig.\ 191. The fourteen Bravais lattices. If we assume spherical symmetry for the lattice points, the space groups of the fourteen Bravais lattices will be (1) P1 (2) P2/m (3) C2/m (4) Pmmm (5) Cmmm (6) Immm (7) Fmmm (8) P6/mmm (9) R3m (10) P4/mmm (11) I4/mmm (12) Pm3m (13) Im3m (14) Fm3m. The capital letters denote the translation groups: P, R primitive lattices; C lattices centred in the face cutting the edge c; F face centred lattices; I body-centred lattices. (1) is triclinic, (2)--(3) monoclinic, (4)--(7) orthorhombic (8) hexagonal (9) trigonal (10)--(11) tetragonal (12)--(14) cubic. A.V.\ Shubnikov and V.A.\ Koptsik, \textit{Symmetry in Science and Art}, Plenum 1974, p.205. \bigskip 680 Crystal Fig.\ 73. The 47 simple forms which crystals may take: (1)--(7) Pyramids; (8)--(14) bipyramids; (15)--(21) prisms (22), (23), (25) tetrahedra; (24), (26), (28) trapezohedra; (27) rhombohedron; (34) scalene triangle; (33), (35) scalenohedra; (31) dihedron; (32) pinacoid; (23), (29), (36)--(47) simple forms of the cubic system; (23) tetrahedron; (29) cube; (30) octahedron; (36) trigonal tristetrahedron; (38) pentagonal tristetrahedron; (39) rhombic dodecahedron; (40) pentagonal dodecahedron; (41) tetrahexahedron; (42) hexatetrahedron; (43) didodecahedron; (44) tetragonal trisoctahedron; (45) trigonal trisoctahedron; (46) pentagonal trisoctahedron (47) hexoctahedron. A.V.\ Shubnikov and V.A.\ Koptsik, \textit{Symmetry in Science and Art}, Plenum 1974, p.205. \bigskip 690 Figs.\ 69 \& 70. Here are two Laue diagrams (Figs.\ 69 and 70), both of zinc-blende from Laue's origianl paper (1912); the pictures are taken in such directions as to exhibit the symmetry around an axis of order 4 and 3 respectively. H. Weyl, \textit{Symmetry}, Princeton University Press 1952. \bigskip 700 Crystal 14. Fluorspar 15. Fluorspar N.\ Wooster, \textit{Semi-precious Stones} (with sixteen coloured plates by Arthur Smith), Penguin 1952 (King Penguin No.\ 65), Plates 14 \& 15. \bigskip 710 Crystal 12. Iron pyrites 13. Fluorspar 'Bluejohn' N.\ Wooster, \textit{Semi-precious Stones} (with sixteen coloured plates by Arthur Smith), Penguin 1952 (King Penguin No.\ 65), Plates 14 \& 15. \bigskip 720 Spiral NAUTILOIDS, GONIATITES AND CERATITES [on left] 64 \textit{Orthoceras} [top left]; 65 \textit{Nautilus} [top right of left]; 66 \textit{Glyphioceras} [bottom left]; 67 \textit{Ceratites}. LIASSIC AMMONITES [on right] 68 \textit{Promicroceras} [top right of left]; 69 \textit{Phylloceras} [top right]; 70 \textit{Dactilioceras} [bottom right of left]; 71 \textit{Harpoceras}. J.F. Kirkaldy (Photographs by Michael Allman), \textit{Fossils in Colour}, Blandford Press 1967, revised 1975. \bigskip 730 Spiral Plate XXXV Shell, Logarithmic Spiral and Gnomonic Growth (Photographs: Kodak Ltd) Plate XXXV gives two examples of X-rayed shells, showing clearly the directing spiral of \textit{Nautilus Pompilius} and the gnomonic growth of \textit{Triton Tritonis} (p.97). Gnomonic growth means growth from inside outwards as opposed to agglutination as is common in crystal [paraphrased from p.90]. M.\ Ghyka, \textit{The Geometry of Art and Life}, Sheed and Ward 1946, reprinted by Dover 1977, p.101. \bigskip 740 Spiral Fig.\ 44. For everybody looking at this picture (Fig.\ 44) of a giant sunflower, \textit{Helianthus maximus}, the florets will naturally arrange themselves into logarithmic spirals of opposite sense of coiling. H.\ Weyl, \textit{Symmetry}, Princeton University Press 1952. \bigskip 750 Helical (334) No. 23 HIGH PETERGATE, c. 1779 (left) (helical) (334) No. 62 LOW PETERGATE, c. 1725 (right) Royal Commission on Historical Monuments, \textit{City of York. Volume 5: The Central Area}, H.M.S.O.\ 1981, Plate 196. \bigskip 760 Helical J.D.\ Watson, \textit{The Double Helix: A New Critical Edition}, Weidenfeld and Nicholson 1981, p.121. \bigskip 770 Helical G. Nass, \textit{The Molecules of Life}, Weidenfeld and Nicholson 1970, p.35. \bigskip 780 Conical spiral HOLOSTOMATOUS AND SIPHONOSTOMATOUS GASTROPODS 110. Left, \textit{Turitella}, Right \textit{Cerithium} Bartonian (Upper Eocene), Gisois, Normandy, $\text{France}\times1\frac{1}{4}$. J.F. Kirkaldy (Photographs by Michael Allman), \textit{Fossils in Colour}, Blandford Press 1967, revised 1975. \end{document} %