May 28, 1915] 



SCIENCE 



807 



of each supporting pier, and the traveling live 

 load shifting the center of combined load forth 

 and back over the middle within a range not ex- 

 ceeding one third of the width of the pier, so that 

 tension is never developed at the edge of the 

 bearing. 



An open joint was made at one end of the sus- 

 pended span to provide for temperature move- 

 ments as well as to keep the cantilevers indepen- 

 dent of each other, but the pressure of the earth 

 fill against the ends of the bridge keeps the joint 

 in contact and makes the bridge a real arch to the 

 extent of that pressure, and giving it, under ordi- 

 nary loads, all the rigidity of an arch. 



The Newark Terminal: Maetin Scheeibee. 

 Cooperation ietween the Physicist and the Engi- 

 neer: Gael Heeing. 



Defining engineering as "applied physics," and 

 stating that the province of the physicist is to 

 discover and formulate the laws of nature, while 

 that of the engineer is to then apply these laws 

 and data to the construction of useful structures 

 — ^the author urges a closer cooperation between 

 them, and shows how much the work of the engi- 

 neer is dependent upon that of the physicist. 



As illustrations of its importance he cites cases 

 in which engineering structures failed due to in- 

 complete statements of the laws of nature in 

 books on physios; or in which in applying the 

 physicist's laws it was found by the engineer that 

 they were faultily stated, resulting in misleading 

 or even wrong results. In other cases the engi- 

 neer discovered new laws which it was the prov- 

 ince of the physicist to have given him, the physi- 

 cist being better equipped and trained for such 

 research than the engineer. 



The physicist taught nothing at all in his books 

 about any internal forces in conductors due to the 

 electric currents flowing through them, yet the 

 engineer in his constructive work found them to 

 exist. Maxwell's famous law of induction, as 

 stated by the physicist, when applied to a specific 

 case gave results which were contrary to the facts, 

 as was found in the constructive work of the 

 engineer. Physics says nothing about axial elec- 

 tromagnetic forces in conductors, yet the engineer 

 finds them to exist. The physicist's work is the 

 foundation of the structure of the engineer, and 

 with an insecure or doubtful foundation, the struc- 

 ture is not dependable. Much time, money and 

 failure can be saved to the engineer if the physi- 

 cist gives him all the necessary data and states the 

 laws of nature correctly and completely. 



Attention is called to cases in which quantita- 

 tive laws of certain physical phenomenon have not 

 yet been established by the physicist. Overlook- 

 ing the distinction between the physical and chem- 

 ical parts of thermo-chemical processes is criti- 

 cized. 



Concerning units for measuring physical quanti- 

 ties, it is shown that the physicist is far ahead 

 of the engineer and the latter would often save 

 himself much work in his calculations by adopting 

 decimal multiples of the absolute units, as was 

 done in the case of the electrical units in which 

 all the conversion factors are made unity by defi- 

 nition. Useless double units should be eliminated, 

 but for some cases double units are advocated for 

 eliminating the factor tt from many calculations. 

 In creating new units, physicists are urged to base 

 them on the absolute system, to avoid the use of 

 conversion factors. The physicist's unit of 

 ' ' brightness ' ' of light is criticized as a physical 

 inconsistency and as being an unnecessary double 

 unit. 



Numerous references are given to articles in 

 which the topics touched upon are discussed more 

 in detail. The author hopes that his illustrations 

 will show the importance and the benefits of a 

 closer cooperation between the physicist and the 

 engineer. 



The fourth session was held on the afternoon of 

 Thursday, December 31, Mr. O. P. Hood in the 

 chair, with an attendance of about 35. The pro- 

 gram of the session was as follows: 



Some Engineering Achievements in Philadelphia 

 and Environs: Edgae Maebueg. 



The Bydraulio Laboratory of the Civil Engineer- 

 ing Department, University of Pennsylvania — Its 

 Equipment and Operation: William Easby, Jb. 



Some Laboratory Accessories for Materials Test- 

 ing: H. C. Beeey. 



Correct Methods of Creating and Maintaining 

 Channels at the Mouths of Fluvial and Tidal 

 Eivers, and at the Outlets of Inclosed Tidal 

 Areas: Elmee Coethell. 



The Engineers' Interest in Deep Waterways with 

 Special Reference to Mississippi Biver and its 

 Tributaries: Haeey E. Wagnee. 



The Tide Water Outlet of the New TorTc State 

 Barge Canals: D. A. Watt. 

 This paper presents a brief sketch of the work 



now being constructed by the federal government 



at Troy, N. Y., in order to provide a connection 



between tide water in the Hudson Biver and the 



