Note 4 — MOUNTAIN OBSERVATORIES.
Reading edition
Silvered glass is considerably more reflective than speculum-metal, and Mr. Common’s 36-inch mirror can be but slightly inferior in luminous capacity to the Lick objective. It is, however, devoted almost exclusively to celestial photography, in which it has done splendid service. The Paris 4-foot mirror bent under its own weight when placed in the tube in 1875, and has not since been remounted.