It is, for instance, practically impossible to obtain reliable evidence as to the regularity of employment in any industry in the 17th century, and the best approximations and devices we can invent are very poor substitutes for what we really want.
Amongst insects with imperfect metamorphosis the nearest approximations to the true pupa of the Holometabola are to be found in the subimago a From Chittenden, Bull.
The problem of finding a radius vector satisfying this condition is one which can be solved only by successive approximations, or tentatively.
A remarkable feature is the bare statement of a number of very close approximations to the square roots of numbers which are not complete squares.
Hero's expressions for the areas of regular polygons of from 5 to 12 sides in terms of the squares of the sides show interesting approximations to the values of trigonometrical ratios.