Note 56 — Chapter XVI · THE STARS.
Reading edition
About 2 seconds. Sir W. Herschel found the diameter of α Lyræ with a power of 6450 to be 0″·3553. Tycho Brahe, before the invention of telescopes, estimated the diameter of Sirius as 120″. J. D. Cassini, with a telescope 35 feet long, found the diameter of the same star 5″.