NOTEMBEB 22, 1912] 



SCIENCE 



715 



fifteen out of the sixteen lots the failure is 

 higher among the abnormal than among the 

 normal plants. 



The material is classified in only the alter- 

 native categories, normal and ahnormal, or 

 typical and atypical — of which the latter is 

 highly complex, comprising many difl'erent 

 morphological variations in their permuta- 

 tions. Possibly, some types among the atypical 

 show a lower mortality than the typical seed- 

 lings. "When materials are ample I hope to 

 determine approximately the selective value of 

 each of the chief types of variation, both alone 

 and in various combinations. In the mean- 

 time, the data given here may serve to record 

 another case of the quantitative demonstra- 

 tion of a selective death rate. 



J. Aethur Haeris 



Carnegie Institution of Washington 



the domain op computational astronomy 



To THE Editor of Science: In the light of 

 Professor Campbell's criticism (Science, Oc- 

 tober 25) it is to be regretted that I did not 

 state explicitly that the domain of computa- 

 tional astronomy is much larger than that of 

 the determination of orbits. This is so ob- 

 viously true that it did not occur to me that 

 my remarks could be misinterpreted. Let me 

 amend, therefore, with the statement that 

 Buchholz's Klinkerfues's " Theoretische As- 

 tronomie " belongs in the general field of com- 

 putational astronomy. 



My remark that the computational field 

 might perhaps be called the bookkeeping, or 

 auditing, department of astronomy may have 

 been " unfortunate." Since it incurred the 

 criticism of Professor Campbell I feel quite 

 certain it was. But there is nothing in his 

 communication which leads me to doubt its 

 essential accuracy. 



This classification of "theoretical astron- 

 omy," which was made only in the interest of 

 exactness, clearly does not imply any disre- 

 spect for computation which is of great value 

 not only in astronomy but in many other sub- 

 jects. W. D. MacMillan 



Univeesity of Chicago, 

 October 25, 1912 



SCIENTIFIC BOOKS 

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