From Southern Cross to
Download 4.64 Mb.
|
Barrow style dip circle showing operational elements common to dip-circles. Here you can see the point of the dipping needle and the microscopic viewer through which you look to align the cross hair with the needle-point. One then reads off the dip value on the vernier scale using the other lens adjacent to the outer etched ring. All this must be done with whilst keeping the apparatus aligned along the magnetic meridian and, when at sea, in spite of the ship’s movement. The second series of magnetic observations was carried out in permanent or semi-permanent observatories. For example, in the southern hemisphere the astronomical observatories at Cape Town, Melbourne and Christchurch provided service to coordinated magnetic observing programs (until the development of electric tramways whose strong currents interfered with the natural magnetic signature). Semi-permanent observatories were established at the bases established by some of the key expeditions at the turn of the twentieth century, including Scott’s Discovery, Drygalski’s Gauss and Mawson’s Aurora expeditions. These installations consisted of two adjacent huts. Housed within the “absolute” hut was a Kew style magnetometer (a sophisticated and highly precise instrument). Within the “variation” hut there was an instrument that recorded continuous changes in the magnetic elements. This was by means of a clockwork-driven drum that carried a sheet of photographic paper onto which was projected a light beam reflected from the mirrored end of suspended magnets within the apparatus. These “Eschenhagen magnetometers” required daily attention and regular (usually monthly) calibration against results from the absolute instrument. The clockwork mechanism could also be made to drive at an accelerated rate for a higher resolution trace during so-called “term hours” when multiple observing stations carried out “fast run” observations in synchrony. 
Directory: Upload Upload -> 587 Return function, r i(X) r i(0) r i(1) r i(2) r i(3) 1 0 2 4 6 Thermal Station, I 2 0 1 5 6 3 0 3 5 6 10 Upload -> Department of science and humanities department of mathematics part-a questions and answers Upload -> The Case Against the nypd’s Quota-Driven ‘Broken Windows’ Policing What Is It? Upload -> For want of a nail Upload -> Traditional British values Upload -> Tv shows, Made for tv movies, Mini Series & Internet Programs Shot at Paramount Ranch Upload -> Ownership Models There are two different types of ownership models Upload -> Police Militarization Upload -> City of rising star regular meting thursday, july 14, 2016 Upload -> Township of winfield Download 4.64 Mb. Share with your friends:
|