SCIENCE. 



147 



per second depends upon the density, and in solids 

 and liquids this secures the destruction of the funda- 

 mental vibrations as the energy of vibration is in- 

 creased, at the same time developing the multitude of 

 irregular ones shown in the spectrum ; while in a gas 

 the number of impacts per second is many times less 

 than the regular rate of vibration, and this secures the 

 time for either fundamental or harmonics, and the 

 consequent spectra. The number of vibrations n 

 the hydrogen atom makes when the wave length is 



.0131277 mm. will be n =— = 3X IQ = 2 286x1 o 1 ". 



1 -i3 I2 77 



Let v x represent the velocity in free path motion of 

 the atom at o° Cent, and 760 mm. pressure = 1860- 



000 mm. Their amplitude a will equal 



1860000 



= oi34Xio- 

 of the atom 



n 2286x10") 

 m. Comparing this with the diameter 



I 34X I ° 8 — ,x62. That is the ampli- 



5Xio- 



tude is equal to .162, the diameter of the atom at o . 



Assuming a temperature higher than this, say 273° 

 Cent, then the energy of the atom in its free path mo- 

 tion compared with that it has at o° will be as \/-7: 1 

 and 1 : : i860 : 2630 m. per second, and as be 



fore amplitude a will equal — = 



n 



115X10 7 . This compared with 



2286x10'° 

 the diameter 



the atom gives 



115x10'' 



.23. That 



of 

 the 



5Xio 



amplitude is equal to .23 the diameter at 273° Cent, 

 a difference of .068 for 273°. 



With same data the maximum temperature of the 

 hydrogen atom may be calculated for as 



(.162)' : (.78S4) 2 : = 273 : 6419° 

 which would be the highest temperature the atom 

 could have if it could have such an amplitude, and 

 this will be reduced as the thickness of the ring in- 

 creases. Any additional energy the atom would re- 

 ceive could not possibly heat it but would be expended 

 either in rotating it or in giving to it a free path 

 motion. In like manner the amplitude for a single 

 degree is found to be .0098 diameter, or very nearly 

 one-hundredth the diameter. 



For other atoms than hydrogen when they have the 

 same energy their amplitude must vary inversely as 

 their mass, so that for oxygen the amplitude at 273 

 .162 



would be 



16 



= .01 its diameter, and its maxi- 



mum temperature will be 6419x16 = 102704° Cent, 

 a number altogether too high for the same reason 

 as was given for hydrogen, namely it assumes that the 

 ring has no thickness. 



If these computations have any value they may 

 be applied to the solution of the temperature of the 

 sun. 



The elements having the greatest density must have 

 the highest maximum temperature. In the sun 

 twenty-five elements have been determined spectro- 

 scopically and the average density of these twenty- 

 five is 63. Now on the hypothesis that these elements 

 exist in equal quantities in the sun, which is not very 

 probable, the maximum temperature of that body woulp 

 be about 400000° Cent. 



As at absolute zero each atom is quite independent 



of every other atom, that is, matter has not a mole- 

 cular structure, so, at certain high temperatures that 

 differ for different substances, all molecular groupings 

 must be broken up and the atoms are quite dissociated 

 from each other, and this dissociation must occur 

 before the maximum temperature is reached ; it would 

 appear that whenever at the sun the temperature 

 approached its maximum, then the elements would be 

 elementary, uncombined, and if compounds are ob- 

 served or appear probable from phenomena witnessed, 

 that will be the best evidence that the temperature is 

 decidedly lower than the above figure. For hydrogen 

 the dissociation temperature is only about 700 Cent, 

 which is only about one-ninth its maximum. 



MARSH'S ODONTORNITHES* 



Were there no other proofs of his zeal and success 

 in extending the bounds of knowledge, the writer of 

 this magnificent monograph would be famous as — for 

 ten years at least, — the sole discoverer, describer and 

 possessor of the remains of Extinct Toothed Birds of 

 North America. 



It may befall almost any diligent explorer to find 

 the remains of some species previously unknown, but 

 few have had — or so well-deserved — the privilege of 

 presenting to the world a new series of facts embody- 

 ing a new idea, at once easily appreciated by the 

 many, and serving the few as material for profound 

 consideration. That a bird with teeth is, most liter- 

 ally, a rara avis, may be conceded without extensive 

 acquaintance with either Latin or Ornithology ; on 

 the other hand, it is probable that naturalists have 

 not yet wholly realized the import of this fulfillment 

 of a prediction which might have been made legit- 

 imately — though we are not certain that it ever was 

 — at any time during the last twenty years. 



Aside from the Appendix, the present volume em- 

 braces detailed descriptions of the bones and teeth of 

 Hesperornis and Ichthyornis ; a general description of 

 the "Restoration" of each genus; and a "Conclusion" 

 embracing the author's views upon the taxonomic re- 

 lations, and probable evolution of these two forms, to- 

 gether with Archceopteryx. 



The following are the principal characteristics of 

 the two American genera, chiefly as recapitulated 

 upon p. 187. In hesperornis, the articular ends of • 

 the vertebral centra are saddle-shaped, as in recent 

 birds; in Ichthyornis they are biconcave, as in many 

 fishes : Ichthyornis has a prominent sternal keel for 

 the attachment of the muscles of the well- developed 

 wings ; in Hesperornis, the sternum is without a keel, 

 and each wing is represented by only a rudimentary 

 humerus : the wing-bones of Ichthyornis have tuber- 

 cles evidently for the attachment of feathers; no signs 

 of feathers have been observed with Hesperornis, but 

 they doubtless were present in life : in both genera, the 

 caudal vertebras are few, so that the bony tail is short 

 as in recent birds : in both, the mandibular rami seem 

 to have remained permanently ununited by bone : in 

 both, as indicated by casts of the cranial cavity, the 

 prosencephalon was narrower than in recent birds of 



* Odontornithes : A Monograph on the Extinct Toothed Birds of North 

 America ; with thirty-four plates, and forty woodcuts. With an Appendix 

 giving a Synopsis of American Cretaceous Birds. By Othniel Charles 

 Marsh, Professor of Palaeontology in Yale College, Memoirs of the Pea- 

 body Museum of Vale College, vol. i ; pp. 201. This memoir will also 

 form vol. vii, Survey of the 40th parallel. 



