An iron bar shaped like an inverted L projects upwards from each of the yokes, the horizontal portions of the bars being parallel to the rods, and nearly meeting at a height of about 8 in.
For simplicity of calculation, the clear length of each rod between the yokes is made 12.56 (=47r) centimetres, while the coil surrounding the standard bar contains 100 turns; hence the magnetizing force due to a current of n amperes will be ion C.G.S.
Suppose the switches to be adjusted so that the effective number of turns in the variable coil is loo; the magnetizing forces in the two coils will then be equal, and if the test rod is of the same quality as the standard, the flow of induction will be confined entirely to the iron circuit, the two yokes will be at the same magnetic potential, and the compass needle will not be affected.
Of the Mexican and Central American sculpture and architecture a competent judge says that Yucatan and the southern states of Mexico are not rich in sculptures, apart from architecture; but in the valley of Mexico the human figure, animal forms, fanciful life motives in endless variety, were embodied in masks, yokes, tablets, calendars, cylinders, disks, boxes, vases and ornaments.
The relation between the wall paintings of Teotihuacan and ornaments at Chichen Itza, as also the existence of sculptured stone yokes in Teotihuacan, in the country of the Totonacs, in Guatemala.