Professor Pickering has since then reported that bright lines have been found on the plates of forty-one previously known variables of this class, and that more than twenty other stars have been detected as variables by this peculiarity of their spectrum; that is, bright lines being seen in them suggested that the stars were variable, and further Photometric investigations corroborated the fact.
"The Story of the Heavens"
Robert Stawell Ball
This is particularly desirable, when, as in this case, the unaided eye enters into competition with Photometric apparatus, by which, as some think, it should properly be altogether replaced.
"A Plan for Securing Observations of the Variable Stars"
E. C. Pickering
According to recent Photometric measurements it emits seventy times the quantity of light, and is three times more massive than the great luminary of our system.
"The Astronomy of Milton's 'Paradise Lost'"
Thomas Orchard