Roy Soc. f.chf 



Voi7 Xxm .pi: 



- 









|300 































PLATE I 





























i 

















>/ 





PLATE 



E 







250 











f 























/ 



























200 



















1 









/ 





/y^ 









k 

























r 













jf^ 











i 



150 

















? 























s // 



















/ 



i 



W^^Tanperc 



IU/\ t' t nlU"\l 



le 













50 100 200 300 















/ / s m 



w 













K$^ 













1 / 













fr 









7 





y^ 









JRtsistancr. of Platinum 150 



300 



Archibald & Peck Eng'. 5 Edinf 



