164 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ing-point were carried by the ship uniformly in a straight line, 

 and is sufficiently approximate when the compass is placed 

 in the ship's axis of rolling. The perturbation produced in 

 the compass by this rolling will be solely that due to the va- 

 riation of the horizontal component of the ship's magnetic 

 force. Such a position of the compass would have one great 

 advantage, viz., that the application of proper magnetic cor- 

 rectors adjusted by trial, to do away with the rolling error, 

 would also perfectly correct the heeling error. 7 A, XL VIII., 

 364. 



THE FORMATION OF MAGNETS BY ELECTROLYSIS. 



In a recent notice of the labors of Jacobi, Beetz considers 

 the question of the formation of magnets by electrolysis. 

 The latter states that on causing iron to be deposited by gal- 

 vanic action -in the interior of a coil, he subsequently found 

 the iron to be magnetic. To secure this result his cathode was 

 a plain metallic plate, opposed to a similar iron plate which 

 acted as a node. An attempt by Jacobi to produce similar 

 action seems to have failed, and the reason for its failure is 

 explained by Beetz as resulting principally from the fact 

 that the electrodes employed by Jacobi were of such a nat- 

 ure, and so arranged, that it was impossible to induce any 

 magnetism in the iron deposited between them ; in fact, the 

 molecules of the latter were deposited in a magnetic shade 

 so intense that less than 0.01 of the electro-motive force af- 

 fected it. Poggendorff Annalen, CIAI., 486. 



MEASUREMENTS OF TERRESTRIAL MAGNETISM. 



Attention is called by Braun to the practicability of ap- 

 plying the inclinatorium to the determination of the inten- 

 sity of terrestrial magnetism. This was first suggested and 

 applied by Lamont and Lloyd, but seems to have been gen- 

 erally neglected. Braun, however, shows that both theory 

 and practice agree in proving that this method allows of 

 the same degree of accuracy as that attainable by the best 

 magnetometers. In detail he finds that Lloyd's method 

 gives the total intensity more accurately than the horizontal 

 intensity, but by the magnetometer method the reverse is 

 the case. The accuracy of the results obtained by Braun 

 is attributed, in part, to the great perfection of the inch- 



