Encyclopædia britannica : or, A dictionary of arts, sciences, and miscellaneous literature : constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises or systems .. . at marked ^oo^ are parallellines forming nine divifions, each divifion the looothof an inch ; the middle divifion is again divided into5, making divifions to the 5000th of an inch. Thatmarked io,oco is divided in the fame manner, withthe middle divifion divided into 10, making thelOjOOGth of an inch. Example : The glafs micrometer without any mark is alfo di-vided, the outfid
Encyclopædia britannica : or, A dictionary of arts, sciences, and miscellaneous literature : constructed on a plan, by which the different sciences and arts are digested into the form of distinct treatises or systems .. . at marked ^oo^ are parallellines forming nine divifions, each divifion the looothof an inch ; the middle divifion is again divided into5, making divifions to the 5000th of an inch. Thatmarked io,oco is divided in the fame manner, withthe middle divifion divided into 10, making thelOjOOGth of an inch. Example : The glafs micrometer without any mark is alfo di-vided, the outfide lines into icoth, the next intoloocth, and the infide lines into the 4000th of aninch : thefe are again croffed with an equal number of lines in the fame manner, making fquares of thelocth, loccth, and 400c th of an inch, thus demonftra-ting each others fize. The middle fquare of the ioo> thof an inch (fee fig. i6.) is divided into fixteen fquares; now (e) It will be necelTary, for great accuracy, as well as for comparative obfervations, that the two-feet rule(hould always be placed at a certain diftance from the eye; eight inches would, in general, be a proper dif-tance. MIC R O SCOPE fS^UX. ,_^ Plate CCXCVU. t :/.£U//^;.,. fr,/^^,6>/ir/i/. M I C [ 709 ] M I a %/ticreput, now <i9 lOOD fquares in the len2;th of an inch, mul-tiplied by 1000, gives one millioa in an inck furfaoe ;by the fame rule, one of thofe fquares divided into 16mu!l he the fixteen millionth part of an inch furface-See fijj. 26. which is a diminilhed view of the apparentfurface exhibited under the magni ier n^ i of Wilfonsmicrofcope. In viewing the fmalleft lines, Mr Co-ventry ufes n° 2. or 3. ; and they are all better feen,he fays, by candle than by day-light. MICROPUS, BASTARD cudweed: a genus of thepolygamia neceflaria order, belonging to the fynge- aperturs when thi: f;reateft magnifiers are employed. Microfcope EE, three thin plates of brafs within the body of the *~~*, microfcope ; one of
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