NoVEJiBEB 5, 1009] 



SCIENCE 



639 



southeast on contour lines similar to those of 

 the older campus. 



Teachers College, Columbia University, 

 will purchase, at a cost of about $200,000, a 

 ten-acre tract of ground overlooking Van 

 Cortlandt Park, near the terminus of the sub- 

 way. One third of the ground, a natural 

 plateau about forty feet above the level of the 

 park, will be used as an athletic field for the 

 Horace Mann School. The remainder, a finely 

 wooded plateau, about fifty feet higher, will be 

 used for dormitories and houses for in- 

 structors. 



Dr. Donald J. Cowling was installed as 

 president of Carlton College at Northfield, 

 Minn., on October 18. 



Dr. William Arnold Shanklin will be in- 

 stalled as president of Wesleyan University 

 on November 12. 



Mr. Stewart J. Lloyd has been made 

 adjunct professor of chemistry at the Uni- 

 versity of Alabama. 



Leon H. Pennington, A.B. (Michigan, '07), 

 Ph.D. ('09), has been appointed instructor in 

 botany in Northwestern University. 



At Wellesley College the following promo- 

 tions have been made: Elizabeth Plorette 

 Fisher, B.S., from associate professor to pro- 

 fessor of geology ; Lincoln Ware Eiddle, Ph.D., 

 from instructor to associate professor of bot- 

 any; Caroline Burling Thompson, Ph.D., from 

 instructor to associate professor of zoology; 

 Alice Eobertson, Ph.D., from instructor to 

 associate professor of zoology. With the reor- 

 ganization of the department of physical edu- 

 cation Amy Morris Homans, M.A., formerly 

 director of the Boston Normal School of Gym- 

 nastics, becomes head of the department of 

 hygiene and physical education. Miss Homans 

 is joined in this work by Dr. Frederick Pratt, 

 instructor in biology and hygiene, and Dr. 

 Louis Collin, instructor in applied anatomy. 



DISCnSSION AND CORRESPONDENCE 



a reply to dr. PERCrVAL LOWELL 



To THE Editor of Science: Li your issue of 

 September 10, Dr. Percival Lowell alleges that 

 I have made four mistakes in my " Introduc- 



tion to Astronomy," and from these alleged 

 mistakes as premises he draws the unique con- 

 clusion that the planetesimal hypothesis " will 

 not work." Quite apart from the validity of 

 the allegations, it is, to me, a novel idea in 

 logic that errors made in trying to support a 

 proposition become thereby " disproof of it." 

 One might infer by this sort of reasoning that 

 the errors of the class-room have long since 

 destroyed all the principles of mathematics. 

 The logic of the present case is all the more 

 remarkable in that two of the four alleged 

 mistakes do not occur in my discussion of the 

 planetesimal hypothesis at all, while the two 

 that do relate to it are really one, and it is not 

 sliown that even this one has any critical re- 

 lations to the hypothesis. 



The first point raised by Dr. Lowell is in 

 reference to the greatest and least velocities 

 which meteors moving in parabolic orbits can 

 have relatively to the earth, and in this dis- 

 cussion, which appears eighty-three pages be- 

 fore I have mentioned the planetesimal hy- 

 pothesis, I have made an error for which I 

 offer no excuse. In fact, it was quite inex- 

 cusable because I had fully treated, four years 

 earlier, in my " Celestial Mechanics " (chapter 

 VII.), the question of the motion of an 

 infinitesimal body relatively to that of two 

 finite bodies describing circles, and the veloc- 

 ity of impact of meteors is only a special case 

 under it. If Dr. Lowell had been as generous 

 in citing this earlier and fuller treatment as 

 in quoting my brief remarks in the " Intro- 

 duction to Astronomy," he could have omitted 

 a considerable part of his own paper in the 

 Astronomical Journal, whose method does not 

 diiler in any essential way from my exposition 

 of the question. In fact, it would have been 

 necessary only to have determined the con- 

 stant of integration of my equation (7), page 

 186. But I made a mistake, and this seems to 

 fix a new principle in logic with a quantitative 

 function : a mistake in expounding one propo- 

 sition, if made within 83 pages of the discus- 

 sion of another proposition, throws discredit 

 on the latter. 



If it were not for the new logic. Dr. Lowell's 

 second indictment would have nothing to do 



