Jour. Sc. Coll. Vol. XI PI. XXX. 



/'Vg. .9. Seïsmtr. Ar(i\-Hij in Iiifofo. 



(Frani ihe 8ih (o Ou- 18fh ceiihiry.) 



I <r- 



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650-693 750-799 850(199 950-999 IOW-1099 1150-1199 1-250-1299 1350-1399 li50-»99 1550-1599 I6SO-I699 1750-1799 



jn = 'finir irv inters'alii. qf 50 ycar.s. 

 y = jVutnhfr <tf rqke.s iltiiing ÜO ifcars. 



