549 
of Edinburgh, Session 1874 - 75 . 
than that just discussed. We ourselves are, however, to a certain 
extent responsible for this judgment. The cause of his misunder- 
standing is the careless structure of our description. By the use 
of a specific term in the second sentence instead of a generic, the 
thermo-electric currents are made to appear to have been used as a 
means of reducing the electromotive force of the magneto-electric 
currents, while in reality the former were substituted for the latter 
in order to obtain currents of low as well as of high electromotive 
force, that is, to reduce the electromotive force of the currents 
employed. The sentence is a parenthesis, in which the words 
“these currents” take, from the structure of the preceding part of 
the description, a narrower meaning than they were intended to 
have. One might almost have expected Professor Beetz to dis- 
cover the defect, rather than adopt the supposition of belief in the 
reduction of the electromotive force of magneto-electric currents by 
means of a thermo-electric pair. 
The oasual remark that the resistance of either a wire or a 
constant cell can be easily measured, Professor Beetz translates 
incorrectly, and, in consequence, criticises unfairly. We did not 
affirm that the resistance of a galvanic cell is quite as easy ( ebenso 
leicht ) to measure as that of a solid body, nor did we mean to say 
that there is yet a perfect means of measurement, but that by 
Wheatstone’s method (in our reference to which Galvanometer is 
printed Electrometer) approximately accurate results may be easily 
obtained. Why then have von Waltenhofen and others tried to 
improve upon Wheatstone? Simply because they think they can 
reduce the already greatly diminished sources of error, or because 
they wish to have a method applicable to both constant and incon- 
stant cells. 
I come next to consider Professor Beetz’ criticism of the method 
of resistance measurement which we used; and it is interesting to 
notice how even he, who, having written what he has written, 
might be expected to take all possible precautions against mistake, 
nevertheless can slip into what he would call, if we had been guilty 
of them, die allerg rob sten Wissens- und Verstandnissirrthiimer. He 
thinks that our method is the same as his own, except that we 
substituted platinum for zinc electrodes, and relied upon the quick- 
ness with which we could make and break contact for the measuring 
