44 



SCIENCE 



[N. S. Vol. LIII. No. 1359 



to subject the arc to the action of a magnetic 

 field in order to produce oscillations. In fact, 

 the oscillations obtained by simply immersing 

 two copper rods in water and starting an arc 

 between them were much more powerful than 

 those produced by a single are in air, and the 

 stability of the wet arc left nothing to be 

 desired. 



This discovery so discouraged Professor 

 Birkeland from pursuing his original line of 

 investigations that the experiments were 

 dropped. 



Anders Bull 



Chicago, III., 

 October 25, 1920 



ROMANCING IN SCIENCE 



To THE Editor of Science : " O tempus I 

 O mores 1 " To one who has used Professor 

 Cajori's book with some confidence, his reply^ 

 to Dr. Partridge is disturbing. Dr. Partridge 

 concluded^ that we do not know exactly what 

 experiment Galileo performed from the lean- 

 ing tower of Pisa. Professor Cajori in reply 

 offers data that (apparently unintentionally) 

 substantiate Dr. Partridge's statement, but he 

 says that it appears to him too sweeping. 



In Professor Cajori's " History of Physics " 

 (p. 32) the following detailed account occurs: 



The first experiments, which Galileo made while 

 he was a young professor at Pisa, were decidedly 

 dramatic. At that time the doctrine that the rate 

 at which a body falls depends upon its weight was 

 generally accepted as true, merely on the author- 

 ity of Aristotle. It was even held that the ac- 

 celeration varies as the weight. Prior to Galileo 

 it did not occur to any one actually to try the ex- 

 periment. The young professor's tests went con- 

 trary to the doctrine held for two thousand years. 

 Allowing for the resistance of the air, he found 

 that all bodies fell at the same rate, and that the 

 distance passed over varied as the square of the 

 time. With all the enthusiasm, courage and im- 

 prudence of youth, the experimenter proclaimed 

 that Aristotle, at that time believed by nearly 

 every one to be verbally inspired, was wrong. 

 Galileo met with opposition, but he decided to give 

 his opponents ocular proof. It seems almost as if 



1 Science, October 29, 1920. 



2 Science, September 17, 1920. 



nature had resorted to an extraordinary freak to 

 furnish Galileo at this critical moment in the his- 

 tory of science, with an unusual convenience for 

 his public demonstration. Yonder tower of Pisa 

 had bent over to facilitate experimentation, from 

 its top, on falling bodies. One morning, before the 

 assembled university, he ascended the leaning 

 tower, and allowed a one pound shot and a one 

 hundred pound shot to fall together. The multi- 

 tude saw the balls start together, fall together and 

 heard them strike the ground together. Some were 

 convinced, others returned to their rooms, con- 

 sulted Aristotle, and, distrusting the evidence of 

 their senses, declared continued allegiance to his 

 doctrine. 



In his reply to Dr. Partridge, Professor 

 Cajori gives " the historical data " and says 

 that from them " it follows that Galileo 

 dropped different weights of a variety of 

 materials and noticed which of them fell 

 faster." 



Now, Mr. Editor, from what data does the 

 above quoted thrilling account follow? And 

 from what data and by what processes may 

 other parts of history be reconstructed by 

 scientists? And from what data must it 

 follow in your readers' minds that Dr. Par- 

 tridge is the scientist guilty of a " declara- 

 tion " that is " too sweeping " ? Eecently it 

 cost me many hours of painstaking experi- 

 mentation to prove that certain improbable 

 statements made in print by a scientist were 

 directly contrary to fact; when the results of 

 the investigation were sent to him, he replied 

 that his had been merely casual remarks! 

 Your correspondent happened to see the fol- 

 lowing in his Montaigne this morning, Fortis 

 imaginatio generat casum — there translated, 

 "A strong imagination begetteth chance." 

 David Wilbur Horn 

 ■ Brtn Mawr, Pennsylvania 



a thrice told tale 

 The conversation which Professor Camj)^ 

 bell describes, in a recent number of Science, 

 as taking place at the eyepiece of the Lick 

 telescope in September, 1912, prompts me to 

 quote the closing paragraph of my article on 

 the mercury telescope which appeared in the 

 Scientific American for March 27, 1909. 



