Pyle (1997) described the verticity
of P6 as an indicator of age in northern shrikes such that greater verticity
of the black-to-white transition was more typical of HY-SY birds.
Where the proposal page refers to "polarity," the finished version chooses instead "verticity
," a reflection of the fact that Gilbert had to coin many of his own terms and that it would not always be wise to render them directly into modern scientific "equivalents," a problem Mottelay had already encountered.
so that piece of iron whilst it is being formed and lengthened out, is affected by the common cause (to wit, the earth); whilst it is returning also from its heated condition to its former temperature, it is imbued with special verticity
in accord of its position."