Flight by machines heavier than air is unpractical and insignificant, if not utterly impossible.

The reports of the eclipse parties not only described the scientific observations in great detail, but also the travels and experiences, and were sometimes marked by a piquancy not common in official documents.

I was taught the alphabet by my aunts before I was four years old, and I was reading the Bible in class and beginning geography when I was six.

Ten decimal places of π are sufficient to give the circumference of the earth to a fraction of an inch, and thirty decimal places would give the circumference of the visible universe to a quantity imperceptible to the most powerful microscope.

My father followed, during most of his life, the precarious occupation of a country school teacher.

As years passed away I have formed the habit of looking back upon that former self as upon another person, the remembrance of whose emotions has been a solace in adversity and added zest to the enjoyment of prosperity.

We are probably nearing the limit of all we can know about astronomy.