Nebulae. Offprint from: Proceedings of the American Philosophical Society, vol. LVI, no. 5, 1917.
[Philadelphia, PA: American Philosophical Society], 1917. First edition, extremely rare separately-paginated offprint, of the paper which "provided the first evidence supporting the expanding-universe theory" (Britannica). In this profoundly significant paper, Slipher reports his finding that, of 25 spiral ‘nebulae’ examined, 21 are receding from us at high velocities, thus anticipating..... More
Item #6189