248 THE SCIENTIFIC WORK OF GEORGE SIMON OHM. 
thanks to Ohmn’s discovery, all is to us clear and evident. The major- 
ity of the galvanists of the day indeed seemed contented in the laby- 
rinth in which they had involved themselves. They did not seize the 
thread of Ariadne which the sharp-sighted investigator seized at last. 
These pioneer services of Ohm at first remained generally unappreci- 
ated. Only individual physicists, like Poggendorff and Schweigger, 
Pfatf and Fechner, recognized their great importance, and with success 
in their work used this new enunciation. It required a foreign impulse 
to win recognition in Germany for his law of the intensity of the current. 
This law is always meant when ‘“Ohm’s law” is referred to. Pouillet 
established Ohim’s law in France by the articles which he published in 
1831 and 1837, five and eleven years, respectively, after Ohim’s discov- 
ery. In spite of this fact Pouillet believed himself the real discoverer, 
because he had found it experimentally. Pouillet believed that Ohm 
had only deduced it mathematically from certain hypothetical premises. 
In France the belief arose that Ohm found his law by simple deduction 
based upon an hypothesis, and then subsequently verified it by experi- 
ment. This belief remains to the present day in spite of frequent con. 
tradictions. It is found to-day not only in French treatises, but, most 
inconceivably, even in widely used German text-books. It would thus 
appear by no means superfluous to set forth the history of Ohm’s great 
discovery, in its actual course and based upon original publications. 
Experimental investigation strives to recognize a law of nature by 
attempting to establish the dependence of the effect in any natural 
phenomenon upon its determining cause. Measurements are made in 
as many individual cases as possible. Then some relation is sought, 
in the shape of an equation, which shall express this dependence and 
re-produce all the individual cases as accurately as possible. In the 
choice of this equation mistakes will occur which can not be immedi- 
ately detected. The one taken may sufficiently conform to the availa- 
ble observations, which may embrace too small a range of the determin- 
ing quantity, and may fail utterly when this range is extended. Then 
it can not be looked upon as the expression of the law of nature sought, 
which must cover all cases without exception. 
Ohm followed this experimental method when, in 1825, he tried to 
establish the law of conduction. He was at that time a teacher in the 
public school (gymnasium) at Cologne. The experiments made for the 
above purpose were described in an article entitled “‘ Preliminary notice 
of the law according to which metals conduct contaet electricity,” 
Schweigger’s Journal, 1825, vol. xLIv. His “ preliminary notice” war 
too hasty. The formula which he proposed is incorrect. It is: 
vm log (1 + z) 
¢ 
wherem m and @ are constants, and v the loss of force on introducing a 
length of wire equal to x. Ohm soon recognized the cause of this 
