powerful turning lathe, worked by a steam-engine in the Royal Ar- 

 senal at Woolwich. This being made to revolve at the rate of 640 

 turns per minute, the needle was deflected out several degrees, and 

 there remained stationary during the motion of the ball, but returned 

 immediately to its original position on ceasing the rotation. On in- 

 verting the motion of the shell, an equal and contrary deflection took 

 place. 



As the law of the phenomena was not evident with this disposition 

 of the apparatus, and the shell was found too heavy for perfect safety, 

 a Shrapnel shell of eight inches diameter was mounted in a proper 

 apparatus (described in the paper), and a number of experiments 

 made ; the law of which, however, still seemed anomalous, till the 

 idea occurred of neutralizing the earth's action on the needle, when 

 the anomalies disappeared, and the general law of the effect was 

 placed in evidence. The needle being made a tangent to the ball, 

 if the motion of the ball was made towards the needle (whatever was 

 the direction of the axis of rotation), the north end of the latter was 

 attracted, and if the contrary way, repelled. In the two extremities 

 of the axis there was found no effect, while in two opposite points, 

 at right angles to the axis, the effect was a maximum, and the di- 

 rection of the needle was to the centre of the ball. 



The author then proceeds to show how all the results, which be- 

 fore appeared anomalous, agree with this general view, and closes 

 his communication with some theoretical views of their general bear- 

 ing on the subject of the earth's magnetism, which he thinks there 

 are strong reasons for believing to be of the induced kind ; and al- 

 though it appears to him doubtful whether the anomalies observed in 

 the variation of the needle on the earth's surface, can ultimately be 

 referred to this cause, yet, he observes, that one condition essential 

 to the production of these phenomena holds good in the case of the 

 earth, viz. the non-coincidence of its polarized axis with that of its 

 diurnal rotation. 



Further Researches on the Preservation of Metals by Electro-chemical 

 Means. By Sir Humphry Davy, Bart. P.R.S. Read June 9, 1 825. 

 [Phil. Trans. 1825, p. 328.] 



After adverting to the general details respecting the protection of 

 the copper sheathing of ships, contained in his former papers, tha 

 President proceeds, in the present communication, to consider the 

 circumstances under which various substances are deposited upon the 

 protecting copper, and their general influence upon its wear, more 

 especially in regard to ships in motion. For this purpose, he availed 

 himself of the use of a steam boat, employed on an expedition to 

 ascertain some points of longitude in the North Seas, and his in- 

 quiries lead to the inference that motion does not affect the nature 

 of the limits and quantity of the protecting metal ; and that, inde- 

 pendently of the chemical, there is likewise a mechanical wear of the 

 copper in sailing. 



