SEC. 10. - ELECTRICITY. 



The coil forms a closed conducting circuit. As the coil revolves about a 

 vertical axis, the horizontal component of the earth's magnetic intensity 

 produces an alternating current in the coil. A very small magnet is sus- 

 pended at the centre of the coil, and is deflected from the magnetic meridian 

 by the current in the coil. When the coil revolves rapidly, the alternations 

 of the current do not produce any sensible vibration of the magnet, and the 

 tangent of the permanent deflection is a measure of the conductivity of the 

 coil. 



1487b. Resistance Coil in an annular brass case, and em- 

 bedded in paraffin. The resistance of the revolving coil was 

 compared with that of this coil during the experiments. 



Prof. Clerk Maxivell. 



1487c. Bridge Arrangement used in the above comparisons. 



Prof. Clerk Maxwell. 



1489. Plate, showing Dr. Bosscha's Method of determin- 

 ing the Ratio of two resistances, with explanatory note. 



J. Bosscha, Professor, Royal Polytechnic School, Delft. 



1490. Plate, showing Dr. Bosscha's Method of determin- 

 ing the Ratio of two electro-motive forces, with explana- 

 tory note. 



J. Bosscha, Professor, Royal Polytechnic School, Delft. 



1491. Cylindrical Condenser for measuring Capacity 



in absolute electrostatic units. Sir W. Thomson. 



1492. Adjustable Disc Condenser, also used as a spark 

 micrometer. Sir W. Thomson. 



1492a. Early Rheostat, given by Faraday to Sir Charles 

 Wheatstone. The Council of King's College,, London. 



1492b. Divided Condenser, as designed by Mfijor Malcolm, 

 R.E., for comparing the electrostatic capacities of cables, the 

 electro-motive force of batteries, &c. Elliott Brothers. 



This condenser is in 12 subdivisions, as follows, viz.: '001, -002, -002, 

 005, -01, -01, -02, -05, -1; 'I, '2, '5 = 1 microfarad; so that any capacity 

 from -- to 1 microfarad can be obtained. 



1493. Rheostat with large copper wire. 



The Council of King's College, London. 



1494. The Original Wheatstone's Bridge, 



The Council of King's College, London. 



1494a. Rheostat (Agometer), with platinum wire. Invented 

 by M. H. Jacobi, in the year 1841. 



Physical Science Cabinet of the Imperial Academy of 

 Sciences, St. Petersburg. 



