On the Determination of the Ohm. All 



completely solved. Comparative results, however, may be 

 found by assuming that the density of the molecules of aether 

 equals those of hydrogen, or is any multiple thereof ; for then 

 the diameter of a molecule of the aether might be found (that 

 of hydrogen being 5*6 x 10~ 10 of a metre) ; and the combined 

 volume in a cubic foot will equal the number of molecules in 

 a cubic foot multiplied by the volume of one molecule, and 

 hence will be found the length of the mean free path and the 

 coefficient of internal friction. 



We conclude, then, that a medium whose density is such 

 that a volume of it equal to about twenty volumes of the 

 earth would weigh one pound, and whose tension is such that 

 the pressure on a square mile would be about one pound, and 

 whose specific heat is such that it would require as much heat 

 to raise the temperature of one pound of it 1° F. as it would to 

 raise about 2,300,000,000 tons of water the same amount, 

 will satisfy the requirements of nature in being able to trans- 

 mit a wave of light or heat 186,300 miles per second, and 

 transmit 133 foot-pounds of heat-energy from the sun to the 

 earth each second per square foot of surface normally exposed, 

 and also be everywhere practically non-resisting and sensibly 

 uniform in temperature, density, and elasticity. This medium 

 we call the Luminiferous iEther. 



XL VIII. A Determination of the Ohm. 

 By Prof. F. Himstedt*. 



THROUGH the means placed at my disposal by the Go- 

 vernment of the Grand Duchy of Baden, for the deter- 

 mination of absolute resistance, I have been enabled to carry 

 out a determination of the Ohm according to the method 

 recently published by mef; and beg permission to lay an 

 abstract of my results in the following paper before the Royal 

 Berlin Academy. 



According to the above-mentioned method, the constant 

 divergences of the magnet in the same galvanometer are 

 observed — produced in the one case by means of induction- 

 currents passing in the same direction through the galvano- 

 meter at the rate of n per second ; in the other case by means 

 of a constant current whose strength is a known fraction of 

 the inducing current. Let us call the observed angles of 

 divergence ol x and a 2 , the required resistance r will be found 



* Translated from the Sitzungsberichte der k. Pr. Akad. d. Wissens. 

 Berlin, July 23, 1885. 



t Wied. Ann. Bd. xxii. S. 281 (1884). 



