Nanometre stability of Invar and quartz suspended in catenary

Improvements made to a previously reported strain-meter test base have greatly enhanced its usefulness for investigating the secular stability of earth strain meters. Length change of an Invar wire suspended in catenary has been monitored on the base for several months to a point where no improvement beyond parts in 10 10 h -1 was obtained. Quartz chain hung in a 10 m span catenary, has also been investigated. This has been shown to be superior to Invar, reaching a part in 10 11 stability/hour within weeks of installation. This order of comparative stability compares favourably with the more complex stabilized wavelength laser interferometer strain meters currently considered superior to mechanical methods.