910 



SCIENCE 



[N. S. Vol. XXXI. No. 806 



of the sea bottom as a necessary complement 

 of erosion, and {d) the settling back of the 

 continents in relaxation after periods of fold- 

 ing. 



Following this discussion of principles the 

 author gives a list of the chief strand line 

 displacements with interesting although 

 avowedly crude estimates as to the percentage 

 of the continental plateau submerged at each 

 stage. A graphic presentation of the same 

 conclusions is given in the form of curves on 

 plate 101 at the end of the paper. Barrell 

 contributes a theoretical inquiry as to the ef- 

 fect which radial shortening would have on 

 the rate of the earth's rotation, and on the 

 degree to which a given increase in that rate 

 would cause a heaping of the oceanic waters 

 in the equatorial regions during times of 

 erogenic activity. He finds reason to think 

 that there would be a bulging of nearly 100 

 feet for each mile of radial shortening, which 

 would tend to draw dovm the waters in the 

 polar and temperate regions, to keep it sta- 

 tionary in latitude 35° and to cause a rise 

 of the sea level in the tropics. 



The second and much larger part of the 

 paper contains a systematic account of the dis- 

 tribution and migrations of faunas, the geo- 

 graphic changes, and in some measure the na- 

 ture of the climate and topography during the 

 periods from the Cambrian to the Tertiary. 

 This is illustrated by fifty maps showing the 

 author's interpretation of the geography at 

 each of many stages. To give a summary of 

 this part would not be possible in a review, as 

 it would almost necessitate a rehearsing of 

 the original paper, which is itself much con- 

 densed. The most important general fact to 

 be noted is the radical rearrangement of the 

 geologic time table, which is given, in com- 

 parison with the current classification, as fol- 

 lows. 



From this brief description it is plain that 

 Mr. Schuchert's paper is one of first impor- 

 tance to the student of historical geology. It 

 will be most highly valued as an up-to-date 

 synopsis of the sequence of strata with their 

 contained faunas from the base of the Paleo- 

 zoic to the Tertiary period, and it will serve 



as a hand-book of information for many a 

 stratigrapher whose opportunities and experi- 

 ence have necessarily been less extensive than 

 the author's. 



THE NEW GEOLOGIC TIME TABLE 



Old Classification. New Classification, 



{Georgic ^ 

 ^<=adi? " 

 Ozarkic or Cam- 

 *>"■= [paleozoic. 



f Canadic. 



OrdoTieian or J a ^ . - 

 LowerSilurian|gFf»™i".;: 



t Cincinnatic .. 



""J^Sj^f^^r^jMississippic, 



,Neopaleozoic. 



Ic-taceoua {^;^^± 



[■Eogeoic 



1 Eocene 

 Oligocene 

 Miocene "| 

 Pliocene >Neogenic. 

 Pleistocene J 



Cenozoic. 



Any one who has attempted the construc- 

 tion of paleogeographic maps knows the im- 

 certainties with which the work is beset 

 and the impossibility sometimes of knowing 

 just where a particular shore line should be 

 drawn. Under these circumstances it requires 

 courage to put one's many doubtful views in 

 the unchangeable record form of a map, and 

 Mr. Schuchert is to be commended for what 

 he has done in this way and for his interest- 

 ing table of strand line displacements men- 

 tioned above. The imperfection of these is 

 distinctly recognized in the author's introduc- 

 tory remarks and the aid of other students of 

 the subject is solicited by him in making the 

 maps agree with the progress of future dis- 

 coveries. Doubtless many readers of the 

 paper will, like the reviewer, be disposed to 

 take issue with Mr. Schuchert on many mat- 

 ters of detail, but these are hardly within the 

 province of a review. 



The radical changes in the geologic time 

 scale will probably arouse more differences of 

 opinion than any other single feature of the 

 article. It may be asked first whether each of 



