C. Barus — Generic Electrical Relations, etc. 427 



only outcrops of the Cambrian formation of the " Lower " 

 Taconic ; that the " Lower " Taconic includes the " Upper " 

 and is therefore all there is of Taconic. 



It is thus finally made positive that the Taconic system is 

 not a pre-Silurian system, and that the claiming for its equiva- 

 lency with the Huronian was but a leap in the dark. It is 

 manifest, in fact, that " Taconic system " is only a synonym of 

 the older term " Lower Silurian," as this term was used by 

 geologists generally, twenty, thirty and forty years since, and 

 by many writers till a much later date. 



It is almost fifty years since the Taconic system made its 

 abrupt entrance into geological science. Notwithstanding some 

 good points, it has been, through its greater errors, long a hin- 

 drance to progress here and abroad. It has also been a pro- 

 moter of investigations of wide bearing and influence. But, 

 whether the evil or the good has predominated, we may now 

 hope, while heartily honoring Professor Emmons for his earnest 

 geological labors and his discoveries, that Taconic ideas may be 

 allowed to be and remain part of the past. 



1841-1888. 



Art. XLIII. — Certain Generic Electrical Relations of the 

 Alloys of Platinum-* by C. Baeus. 



If the specific electrical resistance (s) of a metal be expressed 

 D y s= f(%i Oj where t is the symbol of temperature and £ a 

 variable parameter, then the data of the present paper may be 

 said to furnish evidence of an inherent physical relation between 

 f(%,0) and/" 7 (^,0) — i. e. the zero values of s and its first derived, 

 function with respect to t, — provided the largest admissible 

 value of % be small in comparison with its maximum value. 

 Usually variations of # are produced by changing the qualities 

 of the originally pure metal by small quantities of some foreign 

 ingredient, metallic or not. With the understanding thus laid 

 down, f\%fi)lf(xfi) is the succinct interpretation of what is 

 ordinarily called temperature-coefficient, and which in the pres- 

 ent paper will often be denoted by a. Conformably with the 

 notation indicated f(0fi) and f'(0,0) are the constants of the 

 unalloyed metal. When this is not thus explicitly stated, I 

 will for the sake of brevity use f(0) and ^'(0) in place of 

 fiXfi) and/XZ' )? respectively. 



* This paper indicates the chief result of the third chapter of the Bulletin on 

 the measurement of high temperatures, to which reference has already been 

 made. (See this Journal, xxxv, p. 407, 1 888.) 



