266 ROCHESTER ACADEMY OF SCIENCE. [April 23, 



Since molien 

 state. 



C) Prof. A. de I-apparent. 80 million years. 



(■') Dr. Alexander Winchell 3 



("') Sir William Thomson 100 " " 



('"j Prof. George H. Darwin 57 " " 



(") Prof. Guthrie Tait 10 



('*) Prof. Simon Newcomb 14 



(") Mr. Clarence King - -. 24 " " 



Excluding the two extreme estimates in the above table, it will 

 be seen that the late estimates are in fair agreement and, as compared 

 with former views, are reasonably definite. There is substantial 

 agreement not only among the geologists, but between the geologists 

 and the physicists. 



Estimates of the relative duration of the greater geologic time 

 divisions have been made as follows : 



Paleozoic. Mesozoic. Cenozoic. 



Dana 12 3 i 



Winchell 931 



Williams, H. S .-. 15 3 i , 



Walcott 12 5 2 



Mr. Walcott's estimate, according to his proportion given above 

 is, for the Paleozoic, 17,500,000 years; Mesozoic, 7,240,000 years; 

 Cenozoic, 2,900,000 years ; total for the fossiliferous sedimentary 

 rocks, 27,650,000 years. 



The time since the departure of the ice of the Glacial period 

 from this portion of the continent has been estimated by several 

 eminent authorities, from different data, and their figures fall within 

 6,000 to iG,ooo years. 



Mr. F. W. ^V'arner described a new ammonia motor now 

 constructing in New York city. 



A letter from Dr. M. A. Veeder was read, relating to the 

 co-operation of the telegraph companies in transmitting reports of 

 auroras and electric disturbances. 



113) de Lapparent: — ^«//. Soc. Cfol. France, 3d Ser., Vol. 18, 1890, pp. 351-355- 



(14) Winchell :— " World Life," 1883, p. 378. 



(15} Thomson -.— Trans. Roy. Soc. EdinOitrgk, Vol. XIII, Pt. 1, p. 157 ; " Treatise on .Natural 

 Philosophy" (Thomson and Tait), Appendix D. 



(16) Darwin (G. U.):-J'/iii. Trans. Roy. Soc, Pt. 2, i87q. 



{\^) Tail:— "Recent Advances in Physical Science," 3d Ed., 1885, p. 169. 



(18) Newcomb:—" Popular Astronomy." pp. 505-519. 



(19) VJvR^:— Amer.Jour. Set., Vol. XLV, January, 1893, pp. i-zo. 



