June 18, 1920] 



SCIENCE 



615 



VACANCIES IN THE GRADE OF ASSISTANT 

 CIVIL ENGINEER, U. S. NAVY 



AppiCATiONS are being received at the 

 Bureau of Yards and Docks, ISTavy Depart- 

 ment, Washington, D. C, to fill 30 vacancies, 

 more or less, in the commissioned grade of 

 assistant civil engineer, TJ. S. Navy, with the 

 rank of lieutenant (junior grade). The pay 

 and allowances at entrance are approximately 

 $3,200 per anmmi, with increases up to $9,000, 

 depending upon length of service and pro- 

 motions. 



The candidate must be an American citi- 

 zen, between the ages of 21 and 34 years on 

 August 1, 1920; must have received a degree 

 in engineering from a college or university of 

 recognized standing; must have had not less 

 than 13 months' practical professional experi- 

 ence since graduation, and must be of good 

 moral character and repute. 



The preliminary examination to determine 

 general fitness will be based on papers sub- 

 mitted by the candidates, reaching the Board 

 on or before August 23, 1920, covering college 

 record, testimonials, references and profes- 

 sional experience. The candidate is not re- 

 quired to report in person for the preliminary 

 examination. Physical examination by a 

 board of medical examiners will be made of 

 those candidates who qualify in the prelim- 

 inary examination. 



Those who qualify in the preliminary and 

 physical examinations will take the final oral 

 and written examinations to be held in Wash- 

 ington, D. C, as soon as possible after the 

 preliminary examination papers have been 

 passed on by the Board. 



Officers of the Corps of Civil Engineers are 

 detailed principally to the various navy yards 

 and naval stations to supervise the work 

 under the Bureau of Yards and Docks, Navy 

 Department, Washington, D. C, consisting of 

 the design and construction of all the public 

 works of the naval establishment on shore as 

 well as the maintenance and repair of existing 

 structures. The work is exceptionally varied 

 and offers an attractive field for able and am- 

 bitious young engineers. C. W. Parks, 



Chief of Bureau 



ARISTOTLE AND GALILEO ON FALL- 

 ING BODIES 



A DRAMATIC event in the history of physics 

 is Galileo's dropping a one pound shot and a 

 hundred pound shot together from the lean- 

 ing tower of Pisa, to disprove Aristotle's law 

 of falling bodies. In 1913 Professor H. H. 

 Turner of Oxford, in a lecture at the Eoyal 

 Institution, quoted Galileo's version of Aris- 

 totle's law: 



Aristotle said that a weight of ten pounds, for 

 example, xell ten times as fast as a weight of one 

 pound.i 



To this J. H. Hardcastle replied,- " Aris- 

 totle never said this at all"; he refers any 

 one who " wishes to find out for himself " to 

 Aristotle's "Physica," Book IV., cap. 8. He 

 does not quote from Aristotle, but quotes 

 from Thomas Aquinas's commentary on the 

 passage in Aristotle to which this reference 

 points. Accepting Hardcastle's statement, G. 

 Greenhill, William Eamsay and Oliver Lodge 

 arrive at the conclusion^ that Aristotle has 

 been misunderstood. Greenhill interprets 

 Aristotle as teaching "that the terminal 

 velocity of a body in a medium is propor- 

 tional to the weight," a law "justified by 

 Newton in his experiments in St. Paul's"* 

 and exemplified in the motion of " a raindrop 

 or hailstone falling vertically in the air, or 

 of a smoke particle up the chimney"; Galileo 

 discussed an altogether different question, viz., 

 " the start of such a body from rest." Ramsay 

 refers to Ostwald as pointing out that "Aris- 

 totle was much more impressed with the re- 

 tarding effect on the velocity of the mass of 

 the medium through which the falling mass 

 fell, than with the laws of ' free fall.' " Lodge 

 emphasizes " the fact that ' terminal velocity ' 

 is the best instance of Newton's first law of 

 motion in actual operation." 



1 Galileo, ' ' Dialogues concerning two New Sei- 

 enoes" (Ed. Crew and De Salvio), New York, 

 1914, p. 62. 



2 Natu/re [London], Vol. 92, 1914, p. 584. 



3 Nature, Vol. 92, pp. 584, 585, 606. 

 * " Prineipia, " Book II., Prop. 40. 



