Note 88 — Chapter VIII · Watt’s Connexion with Dr. Roebuck—Watt acts as Surveyor and Engineer.
Reading edition
The telescope was mounted with two parallel horizontal hairs in the focus of the eyeglass, crossed by one perpendicular hair. The measuring pole was divided into feet and inches, so that, wrote Watt, “if the hairs comprehend one foot at one chain distance, they will comprehend ten feet at ten chains,” and so on. This invention Watt made in 1770, and used the telescope in his various surveys. Eight years later, in 1778, the Society of Arts awarded to a Mr. Green a premium for precisely the same invention.