constructed it at the Cincinnati Observatory, and made a large 
of interesting experiments on the telegraph line between 
its influence perceptible until complete circulation of eacht has 
taken plaée from pole to pole. The velocity of this circulation 
Prof. Mitchel infers to be about 30,000 miles a second. 
Finally, Fizeau and Gounelle, in a paper published{ last April, 
in the Comptes Rendus of the French Academy, express a want 
of confidence in Walker’s results, and describe experiments of 
their own, made on a circuit of 374 miles—a distance which they 
characterize as enormous, although the circuit used in the first 
Coast Survey experiments of Jan., 1849, extended through 5500 
at stations 380 miles apart in a geodetic line. ‘These gentlemen 
used a method totally different from either. Walker’s or Mitchel’s, 
and found that it gave them 62,000 miles a second, as the veloc- 
~ ity in an iron wire, 4 millimeters in diameter, and 110,000 as the 
“a velocity in a copper wire, 2""-5 in thickness. ‘Their method is 
not unlike that of Jacobi’s experiments$ at St. Petersburg in 1838 
for the determination of the time necessary for the development 
of a galvanic current. The experiments appear to have furnished 
no data for an inference as to whether a signal is necessarily com- — 
: municated to the several parts of the circuit after intervals pro- — 
portionate to the distance, or not. & 
uch is the present state of the theory, to the best of my — 
3 knowledge,—and it will be observed that the views in the most 
fundamental points are far from unanimous. Still greater differ- 
ences of opinion exist in regard to the more special questions. 
experiments of Feb. 4, have, it appears’ to me, furnished 
ample materials for arriving at a decision on very many 0 the © 
vexed points, and without farther introduction, I shall proceed to — 
consider the nature of those experiments, the sources of error, a | 
the amount of error introduced by them. Mr. W. has already 
done this very elegantly in the memoir|| to which I have referred; 
but I will also briefly consider the subject here. It will then be 
more easy to enunciate the questions, to which a discussion of the 
* Astr. Journ. i, p. 13. Astr. Nachr., xxx, p. 325, eee 
| cms Resrenane” ¢ 518, 520, 521. . en 
Comptes Rendus, xxx, p. 437. ; Pogg. Annalen, xlv, p. 281. 
Astr. Journ., i, p. 105. 3s ; - - m sae 
5 
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