## Nikola Tesla Books

Capacity of structure without hood before found with extra coil was 311.2 cm, hence for hood alone we get 366.7-311.2=**55.5 cm.** From first and last reading it appears that the secondary capacities in the two cases were as $! {168 \over 39} $!. Now the capacity of excited system in last reading was

*C'*_{s2} = $! {{0.0351 \times 72,661} \over {2 \times 10^{7}}} $! mfd, or *C'*_{s2} = 144.77 cm.

From this would follow value

*C'*_{s1} = $! {168 \over 39} $! x 114.77 = 494.39 cm.

Hence

*C'*_{s1} - *C'*_{s2} = 494.39 - 114.77 = **379.62 cm.**

This value does not agree quite closely with that before found but the tuning was not quite exact in last case.

**Note:** It now seems that the tuning in all previous cases when structure was determined was made to the first octave instead of to the fundamental tone. **This is to be ascertained.** If this be so then capacity would be much greater.

*304*

November 26

He gives the description of some details of the structure with metal sphere on top. He measures the capacitance of this system in combination with a coil with 344 turns and a new "additional coil". Earlier, on Nov. 7, he performed the capacitance measurement of the same structure, but without protective cover, and with the "additional" and experimental" coils. On Nov. 12 he performed similar measurement with coil of 1314 urns, and on Nov. 26 he recalls results of Nov. 7 with new "additional" coil. In the notes there is one more result with the "additional" coil, with the most improved method of determining resonance (please see Nov. 13). This result, which otherwise is quite different from others, is not mentioned on Nov. 26.

There is a remark at the end of the notes of Nov. 26 when he foresees the possibility of systematic errors in determining the resonant frequency and Tesla emphasized that this has to be checked.