SIR ROBERT HADFIELD, BART. " 13 



As an interesting example of the examination done by Hooke in 

 1664, and simple as this may seem now, I give in Fig. 6 the result 

 of an investigation he carried out on the point of a small needle, 

 which to use his own words, was 



made fo fharp that the naked Eye is unable to diftin- 

 guifli any of its Parts. This, notwithftanding, appeared before his Microfcope as in the 

 Figure at a a, where the very Top of the Needle is {hewn above a Quarter of an Inch 

 broad j not round or flat, but irregular and uneven. 



The whole Piece we have here the Pidure of, (according to the Scale given with it) 

 is little more than the twentieth Part of an Inch in Length, and appeared to the naked 

 Eye exquifitely fmooth and polifhed ; but, as feen by the Microfcope, what a Multitude of 

 Holes and Scratches are difcovered to us.? How uneven and rough the Surface! how void 

 of Beauty ! and how plain a Proof of the Deficiency and Bunglingnefs of Art, whofe Pro- 

 ductions when mofi; laboured, if examined with Organs more acute than thofe by which 

 they were framed, lofe all that fancied Perfe<5tion our Blindnefs made us think they had ! 

 Whereas, in the Works of Nature, the farther, the d.=eper our Difcoveries reach, the 

 more fcnfible we become of their Beauties and Excellencies. 



But to return to the Objed now before us ; A, B, Q reprefent large Hollows and 

 RoughncfTes, like thofe eaten into an Iron-Bar by Ruft and Length of Time. D is fome 

 fmall adventitious Body flicking thereto by Accident. 



b. b. b. fliew the End where thii Tmall Piece of Needle v/as broken ofr, in order to 

 take the better View of it. 



Ai ihirp as a Needle is a common Phrafe, whereby we intend to exprefs the mofl ex- 

 quifite Degree of Sharpnefs ; and, indeed, a Needle has the moft acute Point Art is ca- 

 pable of making, however rude and clumfy it appears when thus examined. But the Mi- 

 crofcope can afibrd us numberlefs Inftmces, in tlie Hairs, Brifilc?, and Claws of Infeds ; 

 and alfo in the Thorns, Hooks, and Hairs of Vegetables, of vifible Points many Thou- 

 fands of times fharper, with a Form and Polilh that proclaim the Omnipotence of the:- 

 Maker. 



Another investigation was carried out by Hooke on the " edge of 

 a razor," and to quote his words. 



Figure reprefents the Edge (about half a Quarter of an Inch long) of a very 

 {harp Razor well fet upon a good Hone, and fo placed between the Objed-Glafs and 

 the Light, that there appeared a Rertedion from the very Edge, which is fhewn by the 

 white Line a, b, c , d, e, f. 



When we fpeak of any thing as extremely keen, we ufually compare it to the Edge 

 of a Razor J but we find, wiicn examined thus, how far from Sharpnefs even a Razor's 

 Edge appears : That it feems a rough Surface, of an unequal Breadth from fide to fide, 

 but fcarce any where narrower than the Back of a pretty thick Knife : That it is neither 

 fmooth, even, nor regular ; for it is fomewhat fharper than elfewhere at d, indented about 

 />, broader and thicker about c, unequal and rugged about e, and mofl: even between ^, b^ 

 and f-, f^ though very far in any Place from being really firaighr. 



The Side immediately below the Edge, and what the naked Eye accounts a Part of it, 

 ^, h^y^ k, had nothing of that Polifh one would imagine Bodies fo fmooth as a Hone and 

 Oil (liould give it ; but was full of innumerable Scratches crofling one another, w^ith Lines 

 here and there, more rugged and deep than the relf, fuch as g, h, y, /', a, occafioned pro- 

 bably by fome fmall Duft falling on the Hone, or fome more flinty Part of the Hone 

 itfelf. 



The other Part of the Razor L L, which had been poliflied on a Grind-flone, appeared 

 like a plowed Field, full of Ridges and Furrows. 



The irregular dark Spot w, w, feemed to be a little Speck of Ruft ; corrofive Juices ge- 

 nerally working in fuch a manner. 



This Examination proves, how rough and unfeemly (had we microfcopic Eyes) thofe 

 Things would appear, which now the Dulnefs of our Sight makes us think extremely 

 neat and curious : And, indeed, it feems impofllble by Art to give a perfedl Smoothnefs 

 to any hard and brittle Body ; for Piitt\\ or any other foft Pov/der, employed to polifli 

 fuch Body, mufl: neceflarily confifb of little hard rough Particles, each whereof cut- 

 ting its Way, muft;confequently leave fome kind of Furrow behind Jt. In fliort, this Ed^^e 

 of a Razor, had it been really as the Microfcope fliews it, would fcarce have ferved to chop 

 Wood, inllead of (having a Man's Beard. 



