264 POPULAR SCIENCE MONTHLY. 



investigator, a graceful and persuasive teacher, and fascinating 

 companion ; that to rare powers and attainments he added a lively 

 sympathy in all the interests of humanity, and a courageous devo- 

 tion to whatever he deemed just and true." 



Besides the reports and books already named and the period- 

 icals he conducted. Prof. Rogers was the author of thirty-seven 

 papers in scientific serial and other publications, he and William 

 B. Rogers of eight, and he and Martin H. Boy^ of one paper. 



He was chosen a member of the American Philosophical Soci- 

 ety, and a member of the Academy of Natural Sciences of Phila- 

 delphia in 1835. He was elected an honorary member of the 

 Boston Society of Natural History in 1842, and participated in 

 discussions at its meetings nearly every year from 1845 till 1858, 

 speaking usually on geological facts or theories. 



Other societies besides those already mentioned of which Prof. 

 Rogers was a member were the Geological Society of London, the 

 Royal Geographical Society, and the Anthropological Society of 

 London. 



M. Albeet Gaudry, in a review of the course of development of ani- 

 mate nature through the geological ages, remarks on a curious analogy 

 between the changes experienced by fishes in the Secondary age and those 

 which modern warships are passing through. As soon as the thought of 

 armoring vessels took efPect, sti'onger projectiles were devised, in order to 

 penetrate the armor. Then the armor had to be strengthened, and just as 

 rapidly as the plates were made thicker, more enormous projectiles were 

 cast; so that the race has culminated in the construction of vessels so heavy 

 that they are almost unmanageable, and thought is turning again toward 

 light, swift boats. With the Secondary fishes, too, offensive arms and de- 

 fensive armor were developed pace by pace. The teeth were modified till 

 they could crush through the hard cuirasses of the ganoids, and the Second- 

 ary beds are characterized by marine animals thus furnished. Powerful 

 grinding teeth are found in the bony and the cartilaginous fishes, and even 

 in many of the massive reptiles of the Trias. The fishes, exposed to ene- 

 mies whose instruments of offense matched their defensive armor, were 

 obliged to seek safety in flight. Their vertebral column became more solid, 

 so as to furnish a strong support to their spinal muscles, and their tails 

 were shortened and broadened so as to become instruments of energetic 

 locomotion. When this transformation was completed, the carnivorous 

 fishes had no more use for crushing teeth, and they have almost disap- 

 peared ; no more marine reptiles with teeth like paving stones are found in 

 the Tertiary beds or in modern times ; and fishes with large teeth working 

 like millstones are rare in comparison to those which have thin cutting 

 teeth ; and power resides in agility to reach the goal or escape the danger. 

 Existing fishes are marked by an activity that was unknown in the ancient 

 oceans, and justify the observation of Moquen Tandon. that "the agitation 

 and inconstancy of the sea seem to have impressed themselves on the be- 

 ings which live in its waves, in the suppleness, rapidity, and vivacity of 

 their movements." 



