NATURAL PHILOSOPHY. 



165 



and fluids at ordinary temperatures is as follows, pure copper 

 being taken as 100 : — 



Copper wire, 

 Silver " 

 Gold " 

 Iron " 

 Lead « 

 Mercury " 

 Pallad'm " 

 Platinum" 



1.00 



.98 



1.13 



5.63 



10.76 



50.00 



5.50 



6.78 



His experiments with fluids gave the following results : — 



Pure rain water, 40,653,723.00 



Water, 12 parts; sulphuric acid, 1 part, .... 1,305,467.00 



Sulphate of copper, 1 pound per gallon, .... 18,450,000.00 



Saturated solution of common salt, 3,173,000.00 



" " of sulphate of zinc, .... 17,330,000.00 



Nitric acid, 30 B, 1,606,000.00 



The following table gives the specific resistance in ohms (an ohm 

 is an amount of resistance equal to that exerted by one-sixteenth of 

 a mile of common galvanized iron telegraph Vire No. 9) of vari- 

 ous metals and alloys, at 32° Fah., according to the most recent 

 determination of Dr. Matthiessen : — 



NAME OF METALS. 



Silver annealed, 



" hard drawn, 



Copper annealed, 



" hard drawn, . . . . 

 Gold annealed, 



** hard drawn, 



Aluminum annealed, . . . . 



Zinc pressed, 



Platinum annealed, . . . . 



Iron annealed, 



Nickel annealed, 



Tin pressed, 



Lead pressed, 



Mercury liquid, 



Platinum silver alloy, hard or 



annealed, used for standard 



resistance coils, 



German silver, hard or annealed, 



commonly used for resistance 



coils, 



Gold silver alloy, 2 parts gold, 1 



part silver, hard or annealed,. 



Resistance of 

 wire 1 foot 

 long, weigh- 

 ing 1 grain. 



0.2214 

 0.2421 

 0.2064 

 0.2106 

 0.5849 

 0.5950 

 0.06822 

 0.5710 

 3.536 

 1.2425 

 1.0785 

 1.317 

 3.236 

 18.746 



4.243 



2.652 

 2.391 



Resistance of 

 wire 1 foot 

 long,l-1000th 

 inch in diam- 

 eter. 



9.936 

 9.151 

 9.718 

 9.940 

 12.52 

 12.74 

 17.72 

 32.22 

 55.09 

 59.10 

 75.78 

 80.36 

 119.39 

 600.00 



148.35 



127.32 

 66.10 



Approximate per 

 cent, variation in 

 resistance per de- 

 gree, temperature 

 at 20 degrees. 



0.377 ' 



0.388 



0.365 



0.365 



0.365 

 0.387 

 0.072 



0.031 



0.044 

 0.065 



The use of this table is as follows : Suppose it is required to 

 find the resistance at 32° Fah. of a conductor of pure hard copper, 



