The Damned Thing

"Oct. 5.--I can stand it no longer; I have invited Harker to pass a few weeks with me--he has a level head. I can judge from his manner if he thinks me mad.

"Oct. 7.--I have the solution of the problem; it came to me last night--suddenly, as by revelation. How simple--how terribly simple!

"There are sounds that we can not hear. At either end of the scale are notes that stir no chord of that imperfect instrument, the human ear. They are too high or too grave. I have observed a flock of blackbirds occupying an entire treetop--the tops of several trees--and all in full song. Suddenly--in a moment--at absolutely the same instant--all spring into the air and fly away. How?