b'Member recollectionsASEG newsPaleomagnetism of Mt AinslieWith the invaluable support of the RSES palaeomagnetic group (and in particular of David Edwards) it was possible to spend a three hour practical collecting oriented drill core samples near Canberra, for example on the banks of (igneous) Mt Ainslie. A subsequent two hour practical would then be spent at the ANU palaeomagnetic laboratory, measuring the magnetic properties of the samples. Students could calculate the palaeomagnetic latitude and direction of north, and see that the values they obtained differed from the present day. Having their own core samples brought the message home particularly well.In retrospectStudent excursion to the Canberra Magnetic Observatory at Kowen Forest, 8 April 1982, hosted by Peter Hopgood (first at right) and Ron Smith (third from the right). Looking back I see benefits, given this was a teaching course rather than a current into the ground, as well asreadings handed out on a printed page.professional practice course, in having expanding the array as the experimentFrom the set of readings the studentsfundamental principles demonstrated by progressed, was again a distinct benefitcould calculate the magnetic fieldthe simplest of equipment. Even today, in conveying an understanding of howcomponents, thus learning how the biasI expect there are teaching benefits in measurements of earth resistivity werecoils worked. using first principles basic equipment, made. albeit in conjunction with items which Mt Stromlo seismic vault and heat- are latest state of the art.Canberra Magnetic Observatory flow holeAn excursion to the Canberra MagneticAcknowledgementsAn excursion to the ANU seismic vault, Observatory, in Kowen Forest neardriven into the side of a valley near MtI first acknowledge the students who Canberra, worked well as a two hourStromlo, allowed not only an inspectiontook the course. Every lecturer knows excursion, thanks to the cooperation andof the classic and massive seismometershow invaluable are the questions asked, hospitality of observatory staff. installed there, but also the logging forand the discussion points which arise. At the time one instrument at thetemperature of a hole originally drilledAlso I thank the demonstrators, typically observatory was a proton-precessionfor heat flow studies. The hole had beenresearch students from RSES, who again magnetometer, set up with bias coils, todrilled down through the floor of thewould suggest valuable improvements, measure the total magnetic field and alsovault. and without whom the practicals would its components as they changed withLogging the hole for temperature (usingnot have run smoothly. Also, thanks to time. While inspecting the instrument,a portable logger, part of the heat-flowthe experts at the Canberra Magnetic an instructive exercise for studentequipment held by RSES) showed theObservatory and the Palaeomagnetic involvement was to record, as theylocal thermal gradient. Also, and ratherLaboratory, who made our visits so occurred in real time, the five readingspleasingly, when logged carefully overrewarding.as the magnetometer stepped throughits upper several metres the temperatureFinally, I thank Roger Henderson for his its cycle of bias fields. Taking down theirprofile showed the signal of the previousencouragement to write a memories own set of readings gave the students aseason (summer, for an autumn logging)piece for Preview, which has resulted in sense of reality not obtained from a set ofdiffusing down in to the ground. this item.JUNE 2021 PREVIEW 16'