1881.] ^« ' [Cope, 



drogen lines but F are "due to impurities, " * so that the hydrogen spectrum 

 is harmonically connected with the corona line. 



It may be well to recapitulate, in this connection, some of the simple 

 equations which serve to connect the energies of solar and terrestrial rota- 

 tion, planetary revolution, atmospheric limitation, molecular oscillation, 

 cosmical aggregation, and sethereal action : 



1. M : TT r : : «^ : ©J. Note 34. 



2. v^^^p \ Note 34. 



3. v^ = (^y) ^<^*es 33, 37. 



4. Vo = p ( y) ^<^te 17. 



See, also, Proc. Am. Phil. Soc, xii, 392-4 ; xix, 21-5, and Note 16. 



45. Cosmical Significance of the Corona Line. 



Earth being the centre of density in the solar system, its nascent locus 

 should have a time of revolution tt times as great as its own, witb a semi-axis 



2. 



major of ;r^ X 214.45 = 460.002 solar semi-diameters. The corresponding 

 wave-length (Note 37,) is 5321.35, as is shown by the following propor- 

 tion : 



log. 6441.4 : log. 460.002 : : 7612 : 5321.35. 



This differs by less than ^\^ of one per cent, from the geometric wave- 

 length (Note 41), and by less than Jg of one per cent, from Gibbs's measure- 

 ment of the corona line. 



The Systematic Arrangement of the Order Perissodactyla. By E. D. Cope. 

 {Bead before the American Philosophical Society, April 15, 1881.) 



PERISSODACTYLA. 



This, the second great order of the ungulate Mammalia, naturally occu- 

 pies a position between the Amhlypoda and the Artiodactyla. Its lower 

 forms are more specialized in the structure of the feet than the Amblypoda, 

 while its highest types do not reach the perfection of structure seen in the 

 Artiodactyla. This is particularly indicated by the form of the astragalus, 

 which has but one, the tibial trochlea, and never displays the distal one 

 characteristic of the cloven -footed families. The Perissodactyla occupy, 

 as regards their dentition, a position parallel with the Artiodactyla. They 

 are always superior in dental complication to the Proboscidia and the suil- 

 line Artiodactyla, but only one series, that of the horses, reaches the com- 



* lb. p. 530, foot-note. 



