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THE POPULAR SCIENCE MONTHLY 



affinity passes in its lowest degree into the 

 attraction of aggregation." 



As to Mr. Launcelot's paragraph, wherein 

 he states that many metals, other than gold, 



have been reduced to translucent tenuity, 

 your note makes any answer from me un- 

 necessary. George Iles. 

 Montreal, January 22, 1878. 



EDITOR'S TABLE. 



THE PROGRESS OF AMERICAN BIOLOGY. 

 TTTE publish this month the first 

 V V half of the able and interesting 

 address delivered by Prof. Marsh, be- 

 fore the American Association, at Nash- 

 ville, last August, on the "Introduction 

 and Succession of Vertebrate Life in 

 America," and which is the first com- 

 plete edition that has appeared in any- 

 periodical. The paper is, from its na- 

 ture, somewhat technical, but the author 

 could not help that, as, in dealing with 

 newly-discovered forms of life, he is 

 compelled to use new terras a little 

 freely, and to make his account com- 

 plete he includes some lists of genera, 

 which will be of great service to bio- 

 logical students, and should not fright- 

 en off unscientific readers, who will find 

 much to interest them in the general 

 treatment of the subject. There is noth- 

 ing more remarkable in our time than 

 the activity of its scientific thought, 

 and the importance of the new results 

 that are being reached in all the spheres 

 of investigation. Of this, we have a 

 striking illustration in the fact that four 

 months was sufficient almost to anti- 



The interesting point here is, that 

 these are all forms that the evolu- 

 tionist was expecting from our mar- 

 velous Eocky Mountain region, and 

 they show how rapidly the biologi- 

 cal evidence of this theory is accumu- 

 lating. The whole address is indeed a 

 weighty contribution to the literature of 

 this doctrine, as, besides the mere rec- 

 ord of ancient life which it affords, the 

 genealogies of many groups of animals 

 are now traced for the first time. It is 

 well known that Prof. Marsh, by his 

 skill, enterprise, and assiduity, has made 

 the field of the exploration of the West- 

 ern fossil-beds very much his own ; and 

 in this address, which first attempts a 

 summary statement of what is known 

 of the extinct vertebrate life of this 

 continent, he necessarily includes his 

 own results. Among its leading feat- 

 ures there is a discussion of the migra- 

 tions of extinct mammals, and strong 

 evidence is presented (in opposition to 

 previous opinion upon the subject) that 

 North America is really the oldest con- 

 tinent, from which South America, as 

 well as Asia and Europe, derive many 



quate Prof. Marsh's address, and make |of their animals. The author's obser- 

 it necessary to post it up to the begin- 

 ning of the present year, by notes from 

 the author, stating what new things 

 have been discovered since its delivery. 

 Among these are mentioned a new 

 species of fossil fish (Ceratodus), that 

 has recently attracted much scientific 

 attention, and is significant as the 

 first found in the Mesozoic formations 

 of this country. A number of new 

 Jurassic reptiles, some of enormous 

 size, and a new genus (Epihippus), 

 a missing Eocene link in the genealogy 

 of the horse, have also come to light. 



vations have led him also to conclude 

 that there is at present no evidence 

 that any of the supposed bird-tracks of 

 the Connecticut Eiver sandstone were 

 made by birds, but were probably all 

 made by reptiles. In discussing the 

 unsettled question among geologists as 

 to the line between the Cretaceous and 

 Tertiary rocks in the West, Prof. Marsh 

 puts forward a new principle or law as 

 to the value of different kinds of fossils 

 in determining geological age. His in- 

 vestigations show that the higher the 

 grade of life, the better is the evidence 



