176 Sir W. Siemens. [Apr. 26,. 



The following are the results in substituting for the platinum a 

 wire of platinum with 20 per cent, of iridium. 



Diameter of wire '73 to 75 millim. Temperature of room 59° F. 

 Length of wire 100 centims. Current increasing. 











Corre- 





Amperes. 



Yolts. 



Watts. 



Ohms. 



sponding 

 temperature 



Condition. 











of wire. 





2-169 



1-638 



3 -553 



'7552 





Just warm. 



4-652 



3-045 



14-165 



•6546 





Warm. 



6-858 



6-815 



46-742 



•9936 



442° 



Hot. 



10-17 



11 -745 



119 -48 



1-1545 



725 



Chars cotton. 



11 -477 



14-21 



163 -09 



1 -2381 



873 



Dark red. 



12 -932 



16-67 



215-58 



1 -2891 



965 



Eed. 



15-198 



22-04 



334-97 



1 -4502 



1252 



Light red. 



17 -807 



29-00 



516 -40 



1 -6286 



1587 



Yellow. 



20-791 



36-25 



753 -67 



1 7436 



1787 



White. 



Current decreasing. 



16 -762 



24-65 



413-19 



1 -4706 



1289 





14-210 



19 -865 



282 -28 



1 -3980 



1160 





11 -828 



14 -935 



176-65 



1 -2627 



918 





10-62 



12-76 



135-51 



1-2015 



806 





8-40 



8-845 



74 -299 



1 -0530 



545 





5-487 



4-93 



27 051 



•8985 



279 





4-338 



3 625 



15 -725 



•8364 







A second series were taken with the same piece of wire, and the 

 current increased until the wire broke. 

















Corre- 





Amperes. 



Yolts. 



Watts. 



Ohms. 



sponding 

 temperature 



Condition. 

















of wire. 





2 743 



1 



■907 



5 



•23 





•6952 





Just warm. 



7-062 



7 



•005 



49 



•47 





•9919 



439° 



Hot. 



10 -492 



12 



•66 



132 



•86 



1 



•2066 



816 



Chars cotton. 



15 -634 



23 



•69 



370 



•38 



1 



•5153 



1372 



Light red. 



19 324 



33 



•53 



647 



•93 



1 



•7351 



1771 



White. 



21 -044 



37 



99 



799 



•47 



1 



•8053 



1899 





22 -414 



41 



72 



935 



10 



1 



•8613 



2001 





23-913 



45 



19 



1080 



60 



1 



•8898 



2053 



Incandescent. 



25 -475 



49 



91 



1271 



50 



1 



•9592 



2185 





26-33 



53 



70 



1413 



90 



2 



0395 



2325 



Broke into 

 several pieces 

 immediately 

 after reading. 



