In some old roofs the rafters are connected without any intervening ridge-plate, with the result that after Sectional elevation on AA.
The surveyor-general issues also " sectional maps " (1:190,000 and 1:40,000) and so-called " Standard " topographical maps for the thinly peopled west, on scales of 1:250,000 and 1:500,000.
Hence I = M/v = ml/v = m/a, v being the volume and a the sectional area.
When the magnetizing current is twice reversed, so as to complete a cycle, the sum of the two deflections, multiplied by a factor depending upon the sectional area of the specimen and upon the constants of the apparatus, gives the hysteresis for a complete cycle in ergs per cubic centimetre.
For specimens of large sectional area it is necessary to apply corrections in respect of the energy dissipated by eddy currents and in heating the secondary circuit.