度。”
“you remember what are the properties of two similar triangles?“
“yes，“ replied herbert;“their homologous sides are proportional.“
“well， my boy， i have just constructed two similar right-angled triangles; the first， the smallest， has for its sides the perpendicular pole， the distance which separates the little stick from the foot of the pole and my visual ray for hypothenuse; the second has for its sides the perpendicular cliff， the height of which we wish to measure， t