130 



NEGBETTI AND ZAMBRA, HOLBOEN YIADUCT, E.G. 



TERRESTRIAL MAGNETISM. 



FIG. 133. 



134. Magnetograph or Self-Recording Magnetometer (fig. 133), 

 recommended by the Meteorological Committee of the Royal Society and used 

 at KQVV Observatory. This apparatus, invented and arranged by Mr. Beckley, 

 records the variations continually occurring in the Earth's Magnetism by the 

 aid of photography. Three drums or cylinders, to which are attached sheets of 

 sensitised paper, are revolved by a clock movement (seen in the centre of the 

 engraving), and receive the rays of light projected from small mirrors attached 

 to each of the three magnets so arranged as to exhibit all the variations of 

 Magnetic Force, Inclination, Direction, and Intensity. The lights used are Gas 

 Burners or Paraffin Lamps. 



Our limited space will not permit our giving full details of the various 

 mechanical contrivances made use of in this apparatus, which in many 

 respects are somewhat similar to those employed in the Recordiag Barograph, 

 Thermograph, and Hygrometer shown on pages 30 and 78. 



The Magnetograph is supplied by Negretti and Zambra to special order. 



Price 350 to 500 



