Table 1.

Δf in 11 groups of temperature cycles.

Δf1 (Hz)	Δf2 (Hz)	df (Hz)
−1693.333	−1880.200	186.867
−1695.349	−1880.200	184.851
−1694.338	−1891.306	196.968
−1696.354	−1885.244	188.890
−1697.363	−1890.293	192.930
−1701.399	−1892.310	190.911
−1695.337	−1892.310	196.973
−1695.333	−1893.311	197.978
−1698.361	−1893.311	194.950
−1698.358	−1895.327	196.969
−1700.373	−1898.355	197.982