126 CARNEGIE INSTITUTION OF WASHINGTON. 



far this fatigue exceeds the limits which thej' have set as affecting 

 the accuracy aimed at. The immediate improvement in the appa- 

 ratus contemplated is the lengthening of the tube carrying the 

 torsion head, so as to use a suspending wire two meters long instead 

 of one a little over one meter, as at present. This change, coupled 

 with a decrease in the weight of the suspended system, will diminish 

 the elastic fatigue or set. The^^ see no insurmountable obstacle to 

 complete success, but find that much time is consumed in the prelim- 

 inary work before satisfactory and trustworthy results can be obtained. 

 A preliminary report of the work already done was given at the 

 International Electrical Congress in St. Louis. It is hoped that the 

 work may be completed during the academic j^ear 1 904-1 905. 



C. D. Child, Colgate University, Hamilton, N. Y. Grant No. 194. 

 For investigation of the ionization in the neighborhood of a rttcrcury 

 arc in a vaciaim. $50. 



Abstract of Report. — A few measurements were made of the dis- 

 charge from an iron electrode to the arc which was formed in a 

 vacuum between mercury terminals. Further measurements are to 

 be made varying the distance and the potential difference between 

 the electrode and the arc. From this it is hoped that the velocity 

 of the ions may be computed. 



Measurements have also been made of the drop in potential at the 

 anode and that at the cathode and the total potential difference 

 around the arc with mercury, carbon, graphite, iron, and copper 

 electrodes in a vacuum, with various combinations of these in a 

 vacuum, and with carbon, graphite, and iron in hydrogen. Some 

 experiments were also made using an alternating E. M. F. 



Henry Crew, Evanston, 111. Grant No. 10. For stiidy of certain arc 

 spectra. (For first report see Year Book No. 2, p. xxxviii.) $i,coo. 



1. Concerning the preparation of photographic spectrum map of 

 the metallic arc. Dr. Crew sent to the In.stitution amap of the alumin- 

 ium arc which was completed shortly after his last report. In the 

 preparation of this map two new Al.Oa flutings were discovered. 

 During the coming year he hopes to complete a map of the mercury 

 arc, using the same apparatus. 



2. Concerning the E. M. F. of the intermittent metallic arc, the 

 oscillograph made by the Cambridge Scientific Instrument Company 

 enabled him to determine these (E. M. F.) curves very satisfactorily. 



