Note 19 — Chapter VIII

Hersch. 821. Humboldt (Cosmos, iii. 238 and 246,) gives the period as 68 hours 49 minutes, and says that it is 7 or 8 hours in its less bright state. If we could suppose the times of the warning, and of the greatest eclipse, given by Herschel, to be exactly determined, as 31/2 and 1/4, that is, in the proportion of 14 to 1, the darkening body must have its effective breadth 14/15 of that of the star. But this is on the supposition that the orbit of the darkening body has the spectator's eye in its plane; if this be not so, the darkening body may be much larger.