b'Member recollectionsASEG newsGeophysics student practicals around Canberra, half a century ago.hours) and three one hour lectures perThe purpose was to observe the gravity week. The unit ran for one semester anddeficit due to the river valley, and then was given every year, or sometimes everycompare the result with predictions from second year. The first semester was bestsimple models, calculated in advance on for practical exercises as, outside, thethe basis of a topographic map.Canberra autumn is delightful. In contrast the Canberra winter, at the start of theWe found the traffic across the dam second semester, is less appealing. (which also carries a roadway) caused the gravimeter to vibrate. To solve this Designing classes was an interestingproblem we were greatly helped by the task, in the context of the expertiseACT Police. The dam has six buttresses generously contributed from bothand as our party (walking across the the BMR and RSES. With no particulardam) reached each buttress, the police geophysics base in the Department ofstopped the traffic briefly. We then took Geology, setting up practicals from theour next readings, free of the vibrations facilities which Canberra offered was ancaused by cars moving across the dam.Ted Lilleyenjoyable challenge, and my approach Honorary Associate Professorwas to use the equipment and facilities at Research School of Earth Scienceshand. As Canberra and its surroundingsBlack Mountain TowerAustralian National University, Canberraare well-known to a number of PreviewIt was also convenient to take readings Ted.Lilley@anu.edu.au readers, details of these geophysicalat the top of Black Mountain, and at least I arrived in Canberra in Novemberexercises may be of interest. Below Ion one occasion to take the gravimeter 1968 to take up a research fellowshipsketch what were for me the high pointsup the Black Mountain Tower. The tower in the Department of Geophysics andof several of the practicals; some of themswaying in the wind was then a problem Geochemistry of the Research Schooldistinctly Canberra. I hope readers(unfortunately no police available to of Physical Sciences at the Australianwho have done similar things elsewherestop that!)National University (ANU). Such researchwill enjoy being reminded of their own schools were part of the ANU Instituteexperiences.of Advanced Studies. There was anotherSledge hammer seismicpart of the ANU, the School of GeneralFoucault pendulum Making a seismic source by hitting the Studies, and in this part existed theground with a sledgehammer carried Department of Geology, in a Faculty ofWe made a pendulum (a brass cylinderthe benefit that students were actively Science. The School of General Studiessuspended on piano wire, the materialinvolved, instead of merely standing had its origin in the Canberra Universitysupplied by the RSES Workshop). Thisand watching. Capturing the signals College, a college of the University ofpendulum was set up temporarily inthus generated using (industry cast-off) Melbourne, which had been establishedthe stairwell of the Department ofgeophones, and displaying them on in 1929 after the seat of federalGeology. Once timed for 100 swings,a portable cathode ray oscilloscope government moved to Canberra fromthe pendulum and the timer could be(lent by the RSES electronics workshop) Melbourne in 1927 (and brought with itleft going. Then after say a thousandbrought home the concept that Commonwealth public servants studyingswings, an exact number of completeseismology relies on energy transmission. part-time for University of Melbourneswings could be determined from theThe point was further emphasized when degrees). total elapsed time. An improved estimatedifferent students, taking turns with the of the pendulum period resulted, evensledgehammer, invariably turned the The Department of Geology did not havethough the swings had not been counted a geophysicist on staff, and a series ofpractical into a who can get the largest individually. Also, over the longer timesignal contest.guest lectures in geophysics was giventhe pendulum would show the Foucault by members of the Bureau of Mineralcharacteristic, of a rotation of the Resources Geology and Geophysicspendulum plane demonstrating theUsing the Megger(BMR), and the ANU Department ofrotation of the Earth.Geophysics and Geochemistrywhich,The RSES electronics workshop produced in 1973, became the Research School ofa Megger earth insulation tester of the Earth Sciences (RSES). Scrivener Dam profile time. It was housed in a beautifully-made wooden box, and its voltage source I was asked to assist with giving classesThe pendulum demonstrated thewas hand-generated. This instrument in geophysics and happily agreed. Idetermination of absolute gravity, andworked well measuring earth resistivity found I enjoyed lecturing on topics widerrelative gravity was measured with awhen it was connected by cables to four than my research speciality. I continuedWorden gravimeter (which had beenaluminium stakes arranged in a Wenner to contribute over some twenty-fivein the Department of Geophysicsarray, set up on a grassland part of the years, last giving classes in 1994. Whileand Geochemistry for some years). AANU campus.arrangements varied over this time, Imemorable use made of this instrument remember the unit as comprising twowas a traverse across Scrivener Dam, atThe necessary student involvement in practical periods (three hours and twothe western end of Lake Burley Griffin.winding the handle to drive electric 15 PREVIEW JUNE 2021'