January 9, 1903.] 



SCIENCE. 



49 



saving devices in all the various lines of 

 constructional work have certainly exerted 

 a wonderful influence in the upbuilding 

 of her industries. 



Specialization in the manufacture of ma- 

 chine tools and labor-saving devices has fol- 

 lowed closely the segregation of processes 

 in other lines of industry, and thus there 

 has been created a multitude of special 

 machines, each designed to perform some 

 single and often very simple operation. 



Among other significant features the 

 present tendency in the development and 

 use of this class of machinery is marked by 

 the adaptation of compressed air and the 

 application of electric power to machine 

 driving. In the use of compressed air, the 

 facility of adaptation to various require- 

 ments which are in many cases additional 

 to the supply of motive power, is a valuable 

 featiire peculiar to this system and one 

 which is susceptible of extension along 

 many lines. 



The labor cost in most machine shops 

 and other works is so much greater than 

 the cost of power, that any expedient by 

 which the labor cost may be appreciably re- 

 duced is justified, even though the effi- 

 ciency of the agent itself be low. When- 

 ever new methods or agencies cause an 

 increased pz'oduetion with a given outlay 

 for labor, we shall find these methods super- 

 seding the old, even though the cost of the 

 power required be greater than before. 

 The saving of power is a consideration sec- 

 ondary to the advantages and economical 

 output obtained by its use. 



While economy in the use of power 

 should therefore be secondary to increased 

 output, yet careful attention to details will 

 often greatly reduce the useless waste of 

 power. 



Engineers have recognized for some time 

 past that there is a very great percentage 

 of loss due to shaft friction, which, in 



railroad and other shops where the build- 

 ings are more or less scattered, may be as 

 great as 75 per cent, of the total power 

 used. In two cases known to the speaker 

 these losses are 80 and 93 per cent., re- 

 spectively. In the ordinai-y machine shop 

 this loss will probably average from 40 to 

 50 per cent. No matter how well a long 

 line of shafting may have been erected, it 

 soon loses its alignment and the power 

 necessary to rotate it is increased. 



In machine shops with a line of main 

 shafting running down the center of a 

 room, connected by short belts with in- 

 numerable counter-shafts on either side, 

 often by more than one belt and, as fre- 

 quently happens, also connected to one or 

 more auxiliary shafts which drive other 

 countershafts, Ave can see why the power re- 

 quired to drive this shafting should be so 

 large. There is no doubt, however, that a 

 large percentage of the power now spent in 

 overcoming the friction of shafting in ordi- 

 nary practice could be made available for 

 useful work if much of the present cum- 

 brous lines of shafting were removed. 



Manufacturers are realizing the loss of 

 power which ensues from the present sys- 

 tem of transmission, and we find a gen- 

 eral tendency to introduce difi'erent 

 methods by which a part of this loss will 

 be obviated. Among these are the intro- 

 duction of hollow and lighter shafting, 

 higher speeds and lighter pulleys, roller 

 bearings in shaft hangers, and the total 

 or partial elimination of the shafting. 



Independent motors are often employed 

 to drive sections of shafting and isolated 

 machines, and among these we find steam- 

 and gas-engines, electric motors, com- 

 pressed air and hydraulic motors, although 

 the latter have not been used for this pur- 

 pose to any appreciable extent. 



In the choice of motors, until quite rr- 

 eently the steam-engine has heretofore been 



