238 NATURAL SCIENCE. April, 1896. 



screws be turned through any angle, the magnitude and direction of 

 the tilt given to the stand can be easily determined. The first screw 

 tilts the axis of rotation in the plane of the pendulum, and its object 

 is, therefore, to regulate the sensitiveness of the instrument. If either 

 of the other two screws is turned through a known amount, the angle 

 through which the axis of rotation is tilted in a perpendicular 

 direction is ascertainable, and the corresponding deflection of the 

 point of light on the scale or photographic paper can be measured. 



REFERENCES. 



1. Barrett and Brown. — "Practical Physics," p. 241 ; 1892. 



2. Darisin, G. H. and H. — " On an instrument for detecting and measuring 



small changes in the direction of the force of gravity." Brit. Assoc. Rep., 

 1881, pp. 93-112 ; 1882. 



3. Dar-win, H. — "A Bifilar Pendulum." Seismol. Journ. of Japan, vol. iii., 



pp. 61-63 ; 1894. 



4. Davison, C. — "Report of the Earth Tremors Committee." Brit. Assoc. Rep. 



1893 (bifilar pendulum, pp. 291-299 ; horizontal pendulum, pp. 303-308) ; 

 1894. 



5. . — " Bifilar Pendulum for Measuring Earth-Tilts." Nature, 



vol. 1., pp. 246-249 ; 1894. 



6. Gerard, A. — " On Pendulum Observations." Edinburgh Neiv Phil. Journ., 



vol. Iv., pp. 14-16 ; 1853. 



7. Kennedy, C. — " A Few Chapters in Astronomy"; chapter vi.. The "Hori- 



zontal " Pendulum ; 1894. 



8. Milne, J. — " Reports of the Committee on the Earthquake and Volcanic 



Phenomena of Japan." Brit. Assoc. Rep., 1892 (horizontal pendulum, 

 pp. 107-109) ; 1S93. Also 1895, PP- 84-110 and 115-147; 1896. Seismol. 

 Journ. of Japan, vol. i., pp. 88-90 ; 1893. 



9. . — "A Note on Horizontal Pendulums." Seismol. Journ. of Japan, 



vol. iii., pp. 55-60 ; 1894. 



10. Perrot. — [Les principes de deux appareils destines a rendre manifestes et 



mesurables les variations occasionnees dans I'intensite et la direction de la 

 pesanteur a la surface de la terre, par les divers mouvements de notre globe 

 et I'attraction des corps celestes] . Paris Acad. Sci. Compt. Rend., vol. liv., 

 pp. 728-729, 851-852 ; 1862. 



11. Rebeur-Pasch'witz, E. von — "Das Horizontalpendel und seine Anvven- 



dung zur Beobachtung der absoluten und relativen Richtungs-Aenderun- 

 gen der Lothlinie." Nova Acta Leop. -Car. Akad.,'Bd.. \\.,'p^. 1-216; (hori- 

 zontal pendulum, pp. 17-41, 213-216) ; 1892. 



12. . — " Description of an Apparatus for Recording 



by Photography the Motions of Horizontal Pendulums." Seismol. Journ. of 

 Japan, vol. iii., pp. 35-54 ; 1894. 



13. . — " Horizontalpendel-Beobachtungen auf der 



Kaiserlichen Universitats-Sternwarte zu Strassburg, 1892-1894." Beitrdge 

 zur Geophysih, Bd. ii., pp. 211-535, especially pp. 211-274 ; 1895. 



14. Safarik. — " A Contribution to the History of the Horizontal Pendulum " 



[trans.]. P/;//. Ma^"., vol. xlvi., pp. 412-416 ; 1873. 



15. Wolf, C. — " Sur un appareil propre a I'etude des mouvements du sol." Paris 



Acad. Sci. Compt. Rend., vol. xcvii., pp. 229-234 (Delaunay's pendulum, 

 p. 230); 1883. 



16. Zollner, F.— "On the Origin of the Earth's Magnetism, and the Magnetic 



Rotations of the Heavenly Bodies" [trans.]. Phil. Mag., vol. xliii., 

 pp. 345-365, 446-469, 481-502 (horizontal pendulum, pp. 491-496) ; 1872. 



C. Davison. 

 King Edward's High School, Birmingham. 



