Note 655 — LETTER X.
Reading edition
Voyage dans l'Amer. Merid. i. 212. It may here be observed as a benefit derived by the higher walks of philosophy from insects—that astronomers employ the strongest thread of spiders, the one namely that supports the web, for the divisions of the micrometer. By its ductility this thread acquires about a fifth of its ordinary length. Nouv. Dict. d'Hist. Nat. ii. 280.