February 11, 1916] 



SCIENCE 



189 



immediately enabled Pascal (1647) to 

 prove the falsity of this principle and to 

 establish the correct foundation for the 

 theory of hydrostatics. 



The invention of the air pump made pos- 

 sible a whole series of investigations. Re- 

 cently we have been impressed with the 

 invention of several forms of pumps which 

 enable us to obtain very high vacua with 

 great ease and rapidity. The importance 

 of such appliances must not be overlooked. 

 Time is a most important asset for the in- 

 vestigator. 



I wonder whether we appreciate what we 

 owe to the great accessibility and continual 

 improvement in manufactured materials. 

 What a luxury we have in insulated wire! 

 How could we do without glass tubing! 

 We recall with what difficulty Pascal pro- 

 cured a tube for repeating Torricelli's ex- 

 periment. Now we have even quartz tubing 

 and quartz vessels of all kinds. The recent 

 discovery of producing tungsten in a duc- 

 tile form has made that element indispen- 

 sable for some purposes. Pibrox, a new 

 material not yet purchasable, is an improve- 

 ment on all heat insulators. Manganin 

 wire, with its application to all kinds of 

 electrical instruments, has made electrical 

 measurements of high precision compara- 

 tively simple. But it is not necessary to 

 enumerate further. 



Turning now to electricity for our ex- 

 amples, we find that the electroscope has 

 developed from the pith balls and the 

 simple gold leaves into a variety of very 

 sensitive instruments, and the Thomson 

 quadrant electrometer, into that of Dole- 

 zalek. The string electrometer makes it 

 possible, for the first time, to measure rapid 

 changes of a charge. 



One of the great conveniences of a mod- 

 ern laboratory arises from the high state of 

 perfection of current-measuring instru- 

 ments. Galvanometers which are already 



highly developed are still continually being 

 improved. In the moving coil galvanom- 

 eter higher sensitivity is being attained, 

 and efforts are being directed specially to 

 obtaining a greater constancy in the zero 

 reading and a greater uniformity of the 

 radial field. The development of the gal- 

 vanometer and of the methods of its stand- 

 ardization are of extreme importance to 

 research. 



The electric condenser, which was first 

 made without regard to absorption, has 

 gone through the stage where it was con- 

 sidered an improvement to saturate the 

 dielectric with moisture, then where, in the 

 process of construction, the condenser was 

 boiled in a vacuum; to the present method 

 of boiling at the highest possible tempera- 

 ture, and then subjecting to high pressure. 

 Many problems in the development of the 

 condenser still remain to be solved. The 

 better elimination of the absorbed charge 

 would add greatly to its use as a precision 

 standard for the measurement of the elec- 

 tric quantity, and would be of great im- 

 portance wherever condensers are employed 

 with alternating currents. 



The recent developments for excluding 

 moisture from resistance coils, and for 

 rendering them free from capacity and self 

 inductance, show that advancement even 

 in the construction of resistance standards 

 is still in progress. 



The Crookes' tube has resulted in the dis- 

 covery of the X-rays, which are now prov- 

 ing of such great service not only in medi- 

 cine, but in the study of atomic structure 

 and of atomic distributions in crystals. 



The human voice was first transmitted by 

 electricity in 1876. The rapid conquest, 

 since that time, of the almost insurmount- 

 able obstacles of long-distance telephony 

 has been due to progress in many lines of 

 research and to the large number of workers 

 striving for the same end. The present 



