Note 144 — PART V. GENERAL VIEWS RESPECTING THE SOLAR SYSTEM.
Reading edition
It is a striking illustration of this remark, that 5 out of the 11 planets belonging to the system have been discovered only within the last half century. I may farther notice, that, from the year 1637 to 1757, or a period of 120 years, only 30 Comets altogether were observed; whilst from 1757 to 1817, or in exactly half that period, 60 Comets were observed, So much depends on the perfection of instruments!