Geology and Mineralogy . 401 



teeth, and reduction of digits; III. Simultaneous introduction of 

 new forms, or immigration from outside regions; IV. The Pre- 

 dominance of Certain Types ; V. The Convergence and Diver- 

 gence of the Palearctic and Nearctic Faunae. In discussing the 

 geographical distribution of Tertiary forms the original assump- 

 tion is made that the animals of various families and orders have 

 either originated in, or migrated into their present habitat in past 

 time, so that the geological record as to their order of appearance 

 is of first importance. And in investigating the distribution of 

 the present lime he finds it necessary to have an absolutely reli- 

 able correlation time scale for the fossil faunae, and the problem 

 he then sets for investigation is to connect living distribution 

 with distribution in past time and to propose a system which will 

 be in harmony with both sets of facts. The author adopts Sal- 

 ter's classification of geographical areas, and the terms Arctogaea, 

 Notogaea, Neogaea, and makes an interesting distinction between 

 such large tracts of land as have, from their long separation, 

 become the centers of adaptive radiation for orders of mammals, 

 from those smaller regions which have been isolated from each 

 other for shorter periods by climatic or physical barriers. The 

 first group of divisions of the earth's surface are called realms, 

 and these are the main centers of adaptive radiation for the 

 orders of mammals. The smaller divisions he calls regions and 

 they have served as the centers for the radiation of families of 

 mammals. The author closes his paper with a discussion of the 

 sources of migration of mammals to and from the three great 

 realms of the earth as above described. w. 



7. On the Flow of Marble under Pressure. — A series of exper- 

 iments has been carried on by F. D. Adams and J. T. Nicolsok 

 with pure Carrara marble, having as their object the investiga- 

 tion of the conditions under which the flow of rocks may take 

 place when subjected to differential pressure. Their experiments 

 are to be extended later to other limestones, as also to granite and 

 rocks of different types. 



The method of experiment adopted was as follows : heavy 

 wrought iron tubes were constructed of thin strips of Low Moor 

 iron about one-fourth of an inch in thickness ; these were so made 

 that the fibres of the iron ran around the tube. Polished columns 

 of the marble, about an inch or somewhat less in diameter, and 

 an inch and a half in length, were inserted in the iron tubes, 

 under such conditions as to give perfect contact, and to leave an 

 an inch and a quarter of the tube free at each end. Pressures up 

 to 13,000 atmospheres were then exerted upon them by means of 

 an accurately fitting steel plug. The marble was submitted to 

 pressure under four conditions : first, dry, at ordinary tempera- 

 tures, and again at 300° C. and at 400° C. ; also in the presence 

 of moisture at 300° C. The rate at which the pressure was 

 applied was also varied, the time of experiment extending in the 

 different cases between the limits of ten minutes to sixty-four 

 days. 



