. The Quarterly journal of the Geological Society of London. esian oxides show a much more sympathetic Table VIII. 1. 2. 3. 4. 5. 6. SiO, 45-09 42-61 46-40 42-77 40-14 43-16 TiO-> 2-95 263 2-12 2-73 1-93 2-66 M-ih 15-49 14-70 17-14 7-48 325 10-95 Fe203 372 3-37 312 4-51 301 3-77 FeO 7-78 8-59 6-49 10-79 11-83 8-97 MgO 668 11-20 1-98 16-49 29-29 13-84 CaO 8-63 8-54 7-25 8-62 4-40 7-62 5-16 5-91 909 4-41 2-43 4-61 K20 V45 1-14 0-52 0-51 0-43 1-07 H-,0 2-17 0-15 4-48 1-04 3-10 2-69 0-72 1-05 1-36 076 026 0-65 Rest 0-07 0-28 0-21 0-15 Totals 99-84 99-96 100-23 100-32 100-22 99-99 i 1. Aver
. The Quarterly journal of the Geological Society of London. esian oxides show a much more sympathetic Table VIII. 1. 2. 3. 4. 5. 6. SiO, 45-09 42-61 46-40 42-77 40-14 43-16 TiO-> 2-95 263 2-12 2-73 1-93 2-66 M-ih 15-49 14-70 17-14 7-48 325 10-95 Fe203 372 3-37 312 4-51 301 3-77 FeO 7-78 8-59 6-49 10-79 11-83 8-97 MgO 668 11-20 1-98 16-49 29-29 13-84 CaO 8-63 8-54 7-25 8-62 4-40 7-62 5-16 5-91 909 4-41 2-43 4-61 K20 V45 1-14 0-52 0-51 0-43 1-07 H-,0 2-17 0-15 4-48 1-04 3-10 2-69 0-72 1-05 1-36 076 026 0-65 Rest 0-07 0-28 0-21 0-15 Totals 99-84 99-96 100-23 100-32 100-22 99-99 i 1. Average of teschenites. 2. Average of theralites. 3. Average of Average of picrites. 5. Average of peridotites. 6. Average rock of theLugar sill. part 2] PICEITE-TESCHElSriTE SILL OF LUGAE. 119 relation to the maficity, and may accordingly be used as abscisssein a diagram, against which the other oxides may be plotted asordinates (see fig. 6). Just as in dealing with the mineralogicalvariations, it has been found necessary and desirable to average. 10 15 20 25 30 3o PERCENTAGES OF McjO + FoO the chemical composition of the various rock-types for use in thediagram. The averages thus arrived at are given in Table the calculation of these averages most of the chemical com-positions calculated from the graphic analyses have been used,omitting those which duplicate the actual chemical analyses made 120 MR. Or. W. TYRRELL ON THE [vol. lxxii, by Dr. Scott. Thus No. 3 in Table II (p. 104), No. 5, Table IV(p. 110), and No. 5, Table VI (p. 114), have not been used on thisscore. Furthermore, No. 7, Table II, has been omitted, becauseit represents merely a small and unimportant schlieren, whichwould have an effect on the average of the teschenites incommen-surate with its size and importance. The sum of the ferromagnesian oxides being utilized as abscissae,the diagram shows that the order of increasing richness in theseoxides is lugarite, teschenite, theralite, picrite, an
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