N0VEMBBE9, 1900.] 



SCIENCE. 



703 



the new problems presented. Quite re- 

 cently a committee of learned men from 

 Paris, under the leadership of Minister 

 Bourgeoise, visited Charlottenburg for the 

 purpose of examining into the working of 

 the renowned institution located there. 

 Professor Violle, one of the most illustrious 

 physicists of the French capital, accompa- 

 nied the committee. What better evidence 

 of the success of Germany's great institu- 

 tion can be demanded than the consensus 

 of favorable opinion among those best quali- 

 fied to judge that its fruits are already of 

 the highest order of merit, and its imitation 

 by other European nations — the sincerest 

 form of flattery. 



It would not be just to form an estimate 

 of the success of the Reichsanstalt without 

 taking into account its scientific publica- 

 tions. These are numerous and of great 

 value. Most of the reports of work done 

 are made public with of&cial sanction in 

 various scientific and technical journals. 

 During the past year thirty such papers 

 have been published. The detailed ac- 

 counts, however, of the most important 

 undertakings thus far completed are con- 

 tained in three quarto volumes of investi- 

 gations. Among those contained in the 

 first two volumes may be mentioned papers 

 pertaining to thermometry and to units of 

 electrical resistance. 



The investigations in thermometry com- 

 prise such topics as the influence of the glass 

 on the indications of the mercurial ther- 

 mometer, division of the thermometer and 

 determination of the errors of division, de- 

 termination of the coefficient of outer and 

 inner pressure, determination of the mean 

 apparent coefficient of expansion of mer- 

 cury between 0°C. and 100°C. in Jena glass, 

 and investigations relating to the compari- 

 son of mercurial thermometers. 



Four papers of exceptional value relate 

 to normal standards of electrical resistance. 

 They are, the probable value of the ohm 



according to measurements made up to 

 the present time, the determination of the 

 caliber correction for electrical resistance 

 tubes, the normal mercury standard ohm 

 and the normal wire standard ohm of the 

 Reichsanstalt. When one recalls that the 

 ohm as a practical unit of measurement is 

 defined in terms of the resistance of a 

 specified column or thread of mercury, it 

 will readily be seen that the work done at 

 Charlottenburg in this particular field is 

 fundamental in character and of the most 

 universal importance. 



In passing it is worthy of remark that 

 all the standard resistances designed and 

 constructed at the Reichsanstalt are care- 

 fully compared with the mercurial stand- 

 ards early in each year. This custom is 

 in accordance with the action taken by 

 the electrical standards committee of the 

 British Association at Edinburgh in 1892, 

 when the mercurial standard was definitely 

 adopted. At this meeting of the com- 

 mittee, representatives of American, French 

 and German physicists (including von 

 Helmholtz) were invited to sit as members. 

 The methods employed in these comparisons 

 and the forms of the standards are original 

 with the Reichsanstalt. The new forms and 

 methods admit of a combined accuracy and 

 convenience not previously attained. 



In addition to the work done in electrical 

 resistance, the investigation of the silver 

 voltameter and the electromotive force of 

 standard Clark and Weston cells has been 

 highly productive of useful results for the 

 other two fundamental electrical measure- 

 ments. Much remains to be done in this 

 latter direction, for the electromotive force 

 assigned to the Clark and Weston cell, even 

 in the latest report of the Reichsanstalt, is 

 derived from measurements by the silver 

 voltameter, while the electrochemical equiv- 

 alent of silver is in doubt to a greater 

 extent than the electromotive force of the 

 Clark cell. 



