NATURAL PHILOSOPHY. 161 



The author then shows, by exiDeriments, that to ohtain the 

 proijer etiect of sulphur in the battery, it is necessary that the 

 suli)hur should be mixed with a solution of common salt, or with 

 any other salt of soda, or j^robably with any alkaline base ; it is 

 also essential that the sulphur should come in contact with the 

 copper. Experiments showed that this action of sulphur was 

 subject to the fundamental law of the battery ; for, taking into 

 account the traces of sulphui'etted hydrogen which are disen- 

 gaged, and the very small quantity of sulphur which is combined 

 with the copper, the conclusion was arrived at that the zinc dis- 

 solved, and the suljihur combined with the sodium, as protosul- 

 phide, in the exact ratio of their equivalents. Summing up his 

 results, M. Matteucci arrives at the following conclusions : — 



1. That finely-divided sulphur, placed in contact with the elec- 

 tro-negative metal of a battery composed of zinc, copper, and 

 solution of common salt, notably augments the electro-motive 

 force, the constancy and the duration of the battery. It is thus 

 hoped, that, by the employment of sulphur, a voltaic combination 

 may be obtained having many advantages over those batteries 

 which are ordinarily used in industry. 



2. The suljihur, though insoluble, and uncombined, enters into 

 combination with the sodium set free by the electric current. 



The action exercised by the small quantity of sulphide of cop- 

 per which is formed still remains to be exijlained. This action 

 appeal's to be essential to the battery. Instead, however, of offer- 

 ing any theory on this sul)ject, M. Matteucci has undertaken fur- 

 ther experiments to elucidate this point. 



INDUCTION COILS. 



At a recent meeting of the Royal Scottish Society of Arts, held 

 in their hall, George Street, Edinburgh, Sheriff Hallard presiding. 

 Dr. Ferguson read a paper on a new method of constructing 

 induction coils, an abstract of which will be interesting to our 

 readers. One peculiarity of the method consists in coiling the 

 secondary wire round the jjrimary coil, in lengths proportionate 

 to the power of the primary coil at the point where the wire is 

 coiled, there being least at the ends and most in the middle. By 

 this construction, the length of the spark given by the induction 

 coil is not purchased, as it generally is, at the expense of its vol- 

 ume. Another peculiarity is, that the wire is wound in two parts, 

 separated by a diaphx-agm, and the poles stand at the same dis- 

 tance from the primary coil. Both poles are thus alike a power. 

 In the usual arrangement, one pole is weak and the other strong. 

 A coil constructed on this method by Mr. Hart, of College Street, 

 was exhibited, which gave readily dense sparks of eight inches in 

 length. The insulation of the coil has been so applied and pro- 

 tected as to secure the permanent power of the coil. The length 

 of the wire on the secondary bobbin is nearly seven miles. 

 Another paper on a new cun^ent interrupter for the induction coil, 

 also by Dr. Ferguson, was read. In this contrivance, a spiral of 

 copper wire, free to oscillate in the middle, is fixed at its end to 

 14* 



