August 29, 1902.] 



SCIENCE. 



335 



engineering and to the progress of inven- 

 tion, become highly perfected and the next 

 question of the engineer and of the employ- 

 er of power has come to be: 'What new 

 motor can be devised to more perfectly 

 utilize the available energies of nature?' 



5. The serious wastes of the best heat- 

 motors are doubly serious and important 

 in view of the fact that our coal deposits are 

 of limited extent and that however great 

 they may appear, that limit will be attained 

 in one fifth of the time, even with the best 

 practice of to-day, that would be secured 

 could the wastes, now apparently inevitable, 

 be extinguished. Our best steam and gas- 

 engines waste four times as much of the 

 thermal energies supplied them as they util- 

 ize. A substitute for these engines must be 

 sought if they cannot be made thus practi- 

 cally perfect ; but no way is known to which 

 the purely thermodynamic wastes which 

 constitute the greatest obstacle can be pre- 

 vented. 



6. Our existing stores of available energy 

 may possibly be reinforced by more com- 

 plete employment of the water-powers, the 

 wind currents and the internal heat of the 

 earth. Our present wastes of thermal ener- 

 gy might be reduced to comparative insig- 

 nificance could a way be found of imitating 

 nature in the complete utilization of the 

 supply through other processes than ther- 

 modynamic. Nature actually does produce 

 light without heat and apparently, at least, 

 power without thermodynamic wastes; it 

 would seem that man should be able to imi- 

 tate her methods. If this could be done, 

 our electric lighting could be provided or a 

 substitute of similar value obtained that 

 should reduce the wastes, as in the fire-fly 

 and the glow-worm, with one four hun- 

 dredth as much expenditure of energy as 

 now is exacted in the production of light by 

 our usual forms of illiuninant. It would 

 be possible to increase the amount of power 

 derived from a stated quantity of potential 



energy four or five times. Heat drawn 

 from the interior of the earth would pro- 

 vide us with what may be needed by man as 

 long as man can live upon a cooling globe. 



7. When the inventors and discoverers 

 have thus performed their task, 'we shall 

 be assured of a vastly longer persistence of 

 civilization upon the globe, shall be able to 

 employ mechanical power at a fraction of 

 its present cost, shall secure light without 

 heat and of a hundred times greater quan- 

 tity at the same expenditure, shall distrib- 

 ute the electric current for whatever pur- 

 poses at minimum expense, and shall make 

 every civilized nation on the earth many 

 times wealthier and shall extinguish pov- 

 erty and, largely, crime. ' 



On Changes in Form as an Essential Con- 

 sideration in the Theory of Elasticity: 

 Frank H. Cilley, Engineer's Office, 

 New East River Bridge, New York City. 

 While we perceive the necessity of recog- 

 nizing and allowing for large distortions of 

 elastic bodies under load, we are apt to 

 think that, if the distortion be sufficiently 

 small, it is negligible. We are apt to pro- 

 ceed on the supposition that changes in 

 stress and deflection due to an added load 

 are unaffected by the existence of other 

 stresses at the time the load was ap- 

 plied. This is incorrect. Distortions, how- 

 ever small, may seriously modify the 

 change in stress and deflection due to a 

 given load. And the existence of other 

 stresses at the time of the application of the 

 load may be a most important consideration. 

 The consequences of small distortions 

 may be fully taken into account by direct 

 but highly mathematical analysis. But 

 methods of approximation will usually an- 

 swer the same end and be much simpler in 

 single numerical cases. We have only to 

 determine the distortion from the stresses 

 as ordinarily found, and then recalculate 

 the stresses for the changed form. 



