We have before ſhow’d the neceſſary Dependence and Connexion, not only of Geometry and Arithmetick, but of Mechanical Arts and Inſtruments with this Science. This leads us naturally to the Enquiry how they can uſe theſe Inſtruments and Engines for the Obſervation of the Stars, how they can write down ſuch their Obſervations, and perform other Things which we do with our Hands. So that we muſt neceſſarily give them [They have Hands.] Hands, or ſome other Member, as convenient for all those Uſes, inſtead of them. One of the ancient Philoſophers laid ſuch Streſs upon the Uſe and Conveniency of the Hands, that he made no ſcruple to affirm, they were the Cauſe and Foundation of all our Knowledge. By which, I ſuppoſe, he meant no more, than that without their Help and Aſſiſtance Men could never arrive to the Improvement of their Minds in natural Knowledge: And indeed not without Reaſon. For ſuppoſe inſtead of them they had had Hoofs like Horſes or Bullocks given them, they might have laid indeed the Model and Deſign of Cities and Houſes in their Head, but they would never have been able to have built them. They would have had no Subject of Diſcourſe but what belong’d to their Victuals, Marriages, or Self-preſervation. They would have been void of all Knowledge and Memory, and indeed would have been but one degree diſtant from brute Beaſts. What could we invent or imagine that could be ſo exactly accommodated to all the deſign’d Uſes as the Hands are? Elephants can lay hold of, or throw any thing with their Proboſcis, can take up even the ſmalleſt Things from the Ground, and can perform ſuch ſurpriſing Things with it, that it has not very improperly been call’d their Hand, tho’ indeed it is nothing but a Noſe ſomewhat longer than ordinary. Nor do Birds ſhow leſs Art and Deſign in the Uſe of their Bills in the picking up their Meat, and the wonderful Compoſure of their Neſts. But all this is nothing to thoſe Conveniences the Hand is ſo admirably ſuited to; nothing to that amazing Contrivance in its Capacity of being ſtretched, or contracted, or turned to any Part as Occaſion ſhall require. And then, to paſs by that nice Senſe that the Ends of the Fingers are endued with, even to the feeling and diſtinguiſhing moſt ſorts of Bodies in the Dark, what Wiſdom and Art is ſhow’d in the Diſpoſition of the Thumb and Fingers, ſo as to take up or keep faſt hold of any Thing we pleaſe? Either then the Planetary Inhabitants muſt have Hands, or ſomewhat equally convenient, which it is not eaſy to conceive; or elſe we muſt ſay that Nature has been kinder not only to us, but even to Squirrels and Monkeys than them. [And Feet.]