100 ANNUAL OF SCIENTIFIC DISCOVERT. 



Other chanfrcs, is liable to be increased by the often-ropeatcd 

 strokes of iho waves. 



The method usually adopted to coiTect these deviations is, by 

 so plaeing^ bar-uiairnets as to eoniiteract the uiaijnctism of the sliip. 

 But, as every vessel has its own luajjnetie peculiarities, — as in 

 some vessels the error is coni))aratively small, or nearly constant 

 for a considerable time, while in others the amount of deviation 

 chanj^cs <>^reatly and suddt-uly, — the bar-ma irnets, remaining 

 constant in foree, cannot ije relied on to correct the deviation. 

 The prevalent idea among shipmasters, that the deviation was 

 necessarily of the same amount, and opposite in direction on op- 

 posite conrsi'S of tiie vessel, is erroneous, and the placing of the 

 local magnets for correction in consecjuence of no a^'ail. 



It is of great importance that masters of vessels should make a 

 table of errors for at least sixteen points of the compass, with a 

 proper allowance therefor, and frequently verify or correct this 

 table of errors, and test the course daily by means of the azimuth 

 comjiass. If this precaution were used by all masters of vessels, 

 not only would the list of disasters be very greatly reduced, but 

 the length and expense of voj'ages, and the premium of insur- 

 ance, would be diminished. 



ACTION OF SULPHUE IN A NEW FORil OF VOLTAIC BATTERY. 



M. Zyiatteucci communicated to the French Academy of Sci- 

 ences a memoir on the above subject, the chief jjoints of interest 

 in which are as follows : — 



The autlior recently had his attention directed to the action of 

 sulphur in a new form of battery invented by M. Blanc Filipo. 

 This battery has for its positive electrode a plate of zinc plunged in 

 a solution of conmion salt, and for the negative metal a plate of lead 

 covered by electrolysis with a very thin layer of copper; enough 

 flowers of sulphur were then mixed with the liquid in the cell to 

 form a thin paste. The needle of a galvanometer, Avhich had 

 been included in the circuit, immediately began to move upwards : 

 after some hours it i-eached nearly the same deflection as would be 

 shown by employing a Daniell's cell of equal size, and remained 

 at the same degree for four or five days, the circuit being closed 

 during the whole of this time. At the end of this period, the 

 layer of copper was found to have changed into sulphide of cop- 

 per, and the liquid had become highly charged with sulphide of 

 sodium, mixed with traces of sulphide of copper. The only dis- 

 advantage at present connected with this battery appeared to be, 

 that, during its action, a small quantity of sulphuretted hydrogen 

 was liberated : notwithstanding this, it is likely to be a most valu- 

 able instrument for telegraphic purposes. 



M. Matteucci found that plates of platinum, iron, copper, silver, 

 or any other electro-negative metal, when covered with a layer of 

 copper, which is absolutely necessary, gave a constant current, 

 similar to the coated plate of lead. When, instead of copper, the 

 plates were coated with silver or lead, the same action took place, 

 the metal being changed into its sulphide. With copper, how- 

 ever, the action was most prompt, intense, and i^ermanent. 



