10 



Art. 9. -T. Terada : 



Flg. 3, B. 





c) Vertical or Z-Compone7it Instrument (downward taken as 

 positive). Instead of the ordinary Lloyd's balance, a new in- 

 strument was designed and constructed by Prof. Tanakadate and 

 Dr. Kadooka, whicii proved very satisfactory. The magnetic 

 needle (Fig. 3, NS), 4 cm. long and 2 jnm. tliick, was fixed to 

 the lower face of a rectangular plane mirror M (Gx 17x 1 mm.), 



made of fused quartz pkite, platinized on its 



upper suface by means of cathode discliarge. 



1" ' \-s^ The mirror has a i)air of projecting arms aa 



N on l)oth sides, to the pointed ends of wliich 



are Avek.led quartz filtres ^^ of 0'05-0-08 mm. 



diameter. Tlie welding may l)e easily made, 



after some practice, l)y pointing the sharp 



point of a fine oxyhydrogen ßame to the 



spot where the fibre is attached to the arm 



by sliglitlv wetting the surface. The fibres 



yj, i"^' ff '^i"e stretched in EW direction by means 



-^'5r^^ ^"-^ of helical springs SS^-* made of fused quartz 



rod, of which the one end is welded to the 



fibre and the other is rigidly fixed to the brass liolder hh by 



means of solder applied in the cavity for receiving the c^uartz rod. 



By means of the nuts nn, the tension could be adjusted without 



twisting the fibre. By turning the scrcAv t, a slight torsion could 



be given to the fibre, in order to adjust the zero position of the 



mirror. Damping is effected by means of the copper block Dj^, 



which serves also for clamping the suspended system when lifted 



up l;)y means of the screw Ar at the lowest part of the instrument. 



Pr is the reflecting prism originally used in MascarFs vertical 



component instrument for a similar purpose. The inclination of 



the prism could be adjusted by means of the screw i. Dc is the 



desiccator containing calcium chloride and TA a thermometer. 



The points of junction of tlie mirror arm aa with the fibre are 

 originally so adjusted that tlie centre of gravity of the suspended 



1) The spring may be dispensed with, provided that the temperature is kept sufficiently 

 constant, without sensibly impairing the reliability of the instrument, though there is the 

 danger of breaking the fibre by accidental shock given to the instrument during mani- 

 pulation. 



