October 2, 1896.] 



SCIENCE. 



503 



point ; finally a chapter on the teachings of the 

 Bible relative to the subject in hand and another 

 on the present aspects of the theory of evolution 

 in which are considered' a number of naodern 

 theories as to causes of evolution, inheritance 

 and variation. 



These lectures present the evolution idea not 

 from, the theological, but from the scientific point 

 of view. They are largely biological in content 

 and spirit though addressed to theologists. The 

 author does not attempt to prove everything, but 

 takes many elementary principles for granted, 

 among them the truth of the entire doctrine of 

 evolution. One is consequently spared the 

 weariness of listening to a labored argument to 

 prove the truth of fundamental ideas, which 

 everybody, except a few immutables, believes. 

 On the other hand it presents in a clear and 

 suggestive way many of the more recent de- 

 velopments of the evolution idea. It does not 

 purport to be an original contribution to knowl- 

 edge, but it is a valuable and extremely well 

 written book of the ' educational ' type. 



e. g. conklin. 



University of Pennsylvania. 



SCIENTIFIC JOURNALS. 

 THE ASTROPHYSICAL JOURNAL, AUGUST. 



The New Elements of Cleveite Gas : By J. R. 

 E.YDBERG. In referring to the work of Runge 

 Paschen and regarding the reduction of the spec- 

 trum of cleveite gas, the writer recalls the fol- 

 lowing simple law, announced some time ago by 

 himself : The difference between the common limit 

 of the nebulus and the sharp series, and the limit 

 of the corresponding principal series, gives the wave 

 number of the common first term of the sharp and 

 principal series. This law holds good to a con- 

 siderable degree of approximation for the al- 

 kali metals Li, ISTa, K and Rb, which have cor- 

 responding triple series, and is proposed as a 

 criterion of the proper mating of the subordinate 

 with the principal series. If we denote the 

 principal series by Pj and Pj and the subordi- 

 nate sets by Si and S2, and assume that Pj be- 

 longs with Si and Pj with Sj, the law will hold ; 

 otherwise, in general, it will not. 



In the correspondence chosen by Kayser and 

 Runge the criterion is satisfied within the limits 

 of observational error. The values of the first 



terms (in wave numbers, per cm.) of the princi- 

 pal series are as follows < 



Computed. Observed. 



Pa 4857.79 4900.65 



He 9230.22 8950.14 



C- 



0=A 

 — 42.86 

 +280.08 



Although the A's are well within the limits 

 of error for the observation of this first line, 

 which is in the infra-red and must be measured 

 with the bolometer, there is evidence, in the 

 case of He, of a probable disturbance due to 

 the proximity of Na ?^ 11392.5, the sodium lines 

 being strong in the visible spectrum. The 

 author, therefore, concludes that the computed 

 values of the lines ai*e the most accurate. More 

 accurate determinations of the lines in question 

 will be of extreme value in testing this most in- 

 teresting law. 



Attention is also called to another law due to 

 the writer, which seems to show Parhelium to 

 be of uneven and Helium to be of even valency. 



Outlines of a Theory of Spiral and Plane- 

 tary Nebulse : By E. J. Wilczynski. 1. A 

 theory to explain the peculiar formation of 

 spiral nebulse. The writer supposes a mass 

 of nebulous matter to be moving in a circle 

 under the action of a central force. In case the 

 mutual attractions of different parts of the mass 

 upon one another are insufficient to resist dis- 

 tortion, it is shown that the different parts of 

 the mass must be moving in concentric circles, 

 the common center, of course, being the attract- 

 ing body. Under these conditions it is evident, 

 from Kepler's third law, that those portions of 

 the nebulous mass nearest the center of the 

 circles must rotate faster than those furthest 

 away. In this manner a former radial line in 

 the nebula will be distorted into a spiral. 



The writer suggests that this gives us a 

 means of approximating to the age of the nebula 

 (as a spiral). 



2. If a nebula has the shape of a flat disc, 

 then the following differential equation exists 

 between p, the density at any point, r, the dis- 

 tance of the point from the center, and w, the 

 angular velocity of the point, where " and p are 

 both supposed to depend only upon r. 



d^ 

 dr^ 



+ i^^_if^y + 4V 



r dr p \dr I c 



= ^f2c.2 + r^\ 

 c V dt I 



