One hardly knows where, in the history of science, to look for an important movement that had its effective start in so pure and simple an accident as that which led to the building of the great Washington telescope, and went on to the discovery of the satellites of Mars.

Construction of an aerial vehicle which can carry even a single man . . . requires the discovery of some new metal or force. Even with such a discovery, we could not expect one to do more than carry its owner.

The beginning of 1856 found me teaching in the family of a planter named Bryan, residing in Prince George County, Md., some fifteen or twenty miles from Washington.

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

Whenever a total eclipse of the sun was visible in an accessible region parties were sent out to observe it.

The time was not yet ripe for the growth of mathematical science among us, and any development that might have taken place in that direction was rudely stopped by the civil war.

I finally reached the conclusion that mathematics was the study I was best fitted to follow, though I did not clearly see in what way I should turn the subject to account.