Page:Star Lore Of All Ages, 1911.pdf/309

Rh Herschel estimated that it contained 14,000 stars. In a recent photograph of this cluster 50,000 stars are shown in an area of the sky which would be entirely covered by the full moon.

Photographs of this swarm of suns fail to do it justice because of its density. In order to give some idea of the wonderful structure of such a cluster a photograph of the globular cluster ω Centauri in the Southern Hemisphere is here shown. It is estimated that this cluster contains in the neighborhood of ten thousand stars, and within its confines Professor Bailey discovered 128 variable stars. This remarkable photograph was taken at the Southern Station of the Harvard College Observatory at Arequipa, Peru, and the writer is indebted to Prof. E. C. Pickering, Director of the Harvard College Observatory for the print here reproduced.

The stars π, σ, ξ, η Herculis form a figure not unlike a keystone, which serves many as a means of identifying the constellation.