Langley, Samuel Pierpont - Autograph Letter Signed

American astronomer (1834-1906), physicist, inventor of the bolometer and aviation pioneer who built the first mechanically propelled heavier-than-air machine to ever fly. 

Autograph letter signed by him, about personal matters.  Size is 4.4 x 6.9 inches, 1 page, central fold, minor stains, in very good condition.