382 Mr. S. V. Wood on the Effects wpon Animal Life 



your notice, I thought you would perhaps excuse the liberty I 

 take in addressing this communication to you. Gf course it 

 would be quite out of place and equally unnecessary for me to 

 explain the philosophy of the matter here, or the difficulties con- 

 nected with first attempts to break the eye of the habit of focus- 

 ing itself according to the amount of convergence ; but for the 

 delight with which I, as a young student of astronomy, made 

 the above observation, as also for my future independence of all 

 stereoscopes, I feel greatly and entirely indebted to the course of 

 lectures upon light. In performing the second of the two expe- 

 riments named, so perfect a perspective inversion is seen in the 

 case of landscapes, that one feels for the moment endowed with 

 the fabled optical powers of the lynx, men being seen most di- 

 stinctly through brick walls, houses, or even hills. 



Hoping, Sir, that you will excuse the liberty I have taken in 

 thus addressing so long a communication to you, 

 Believe me to be, Sir, 



Yours very respectfully, 



Richard T. Lewis. 



LV. 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 Confi- 

 guration have probably produced. By Searles V. Wood, Jun. 



[Concluded from p. 282.] 



Section 4<—The effect produced by the Post-cretaceous Geogra- 

 phical Changes upon the Secondary Fauna. 



IF the foregoing inferences as to the respective geographical 

 configurations of the secondary and post-cretaceous periods 

 are well founded, the effect of the post-cretaceous changes upon 

 the secondary fauna becomes more readily apparent. 



An alignement of continent such as prevailed during the 

 secondary periods from north to south, would, I conceive, neces- 

 sarily have had the effect of assimilating the fauna of high and 

 low latitudes in a great degree ; a free and uninterrupted pass- 

 age for currents of equatorial water along the coasts up into high 

 latitudes, and the return currents from the poles, would have 

 tended to the modification of the climate of the period, in the 

 same way in which the western coasts of Europe and America are 

 modified at the present day, and have produced that more equable 

 rather than tropical character of climate which, it is now gene- 

 rally considered, characterized the prevalent climate of the second- 

 ary periods. The condition of the extreme lands of South 

 America at the present time exemplifies the effect of the humi- 



