THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



MARCH 1862. 



XXIII. On the Form and Distribution of the Land-tracts during 



the Secondary and Tertiary periods respectively ; and on the 



effects upon Animal Life which great changes in Geographical 



Configuration have probably produced. By Searles V. Wood, 



Jun.* 



Section 1. Introductory. — Section 2. The General Geographical Configuration 

 of the Secondary Period. — Section 3. The Changes in the Geographical Con- 

 figuration which resulted from Post-cretaceous Volcanic Action. — Section 4. 

 The Effect produced by the Post-cretaceous Geographical Changes upon the 

 Secondary Fauna. — Section 5. The Preservation, at the present day, of isolated 

 Remnants of the Secondary Continents, and of the Secondary Fauna inhabiting 

 them. — Section 6. Summary and Conclusion. 



Section 1. — Introductory, 



THE attempt to restore in description the outline of the 

 lands and seas of a past geological period, although but in 

 their broadest features, and from that restoration to draw con- 

 clusions as to results emanating from changes in the distribution 

 of the continental tracts in succeeding periods, will probably in 

 the present state of our knowledge be, by many at least, depre- 

 cated as illusory. The consideration, however, of a few leading 

 principles to be observed in making such an attempt will, I trust, 

 tend to remove from the minds of some such an impression, at 

 least sufficiently so to induce a fair consideration of the views 

 here put forward. 



It is obvious that if any tract, large or small, be submerged or 

 elevated by subterranean action, the relative levels of all parts of 

 the tract would, if that tract were raised or depressed by a force 

 exerted equally on every portion, remain the same, however fre- 

 quently the elevation or depression occurred. Such an elevation 

 or depression is, it is true, dynamically impossible, as all these 

 * Communicated by the Author. 



Phil. Mag % S. 4. Vol. 23. No. 153. March 1862. M 



