Barrow, Isaac, Lectiones opticae & geometricae : in quibus phaenomenon opticorum genuinae rationes investigantur, ac exponuntur: et generalia curvarum linearum symptomata declarantur

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            plicentur rectæ AZ, BZ, CZ, DZ, ad ipſam VD perpendiculares,
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            & </s>
            <s xml:id="echoid-s8855" xml:space="preserve">æquales ſingulæ ſingulis in cono circulorum radiis per eaſdem li-
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            teras deſignatis; </s>
            <s xml:id="echoid-s8856" xml:space="preserve">fiet autem in hoc caſu _Spatium_ VDZ triangulum,
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            quia rectæ AZ, BZ, CZ æqualiter à ſe diſtantes æqualiter increſcunt,
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            id quod trianguli applicatis omninò proprium eſt. </s>
            <s xml:id="echoid-s8857" xml:space="preserve">Hujus autem
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            trianguli, ex datis altitudine VD & </s>
            <s xml:id="echoid-s8858" xml:space="preserve">baſe DZ, dimenſio in promptu
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            eſt. </s>
            <s xml:id="echoid-s8859" xml:space="preserve">Quod ſi ſiat _ut circuli radius: </s>
            <s xml:id="echoid-s8860" xml:space="preserve">Ad circumferentiam ipſius, it à_
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            _triangulum VDZ ad quartum_, erit hoc quartum æquale _Superficiei_
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            _conicæ propoſitæ._ </s>
            <s xml:id="echoid-s8861" xml:space="preserve">Eodem planè modo perquam facilè _Sphæræ
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            , sphæri-_
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            _carúmque portionum Superficies_ (nec, datis & </s>
            <s xml:id="echoid-s8862" xml:space="preserve">præcognitis iis quæ
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            requiruntur, alias quaſlibet hoc modo natas) inveſtigare licet. </s>
            <s xml:id="echoid-s8863" xml:space="preserve">At
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            mihi propoſitum eſt generalioribus tantùm inhærere. </s>
            <s xml:id="echoid-s8864" xml:space="preserve">‖ Hanc autem
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            magnitudinum geneſin æmulatur, & </s>
            <s xml:id="echoid-s8865" xml:space="preserve">affinitate quâdam contingit iſte
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            modus, quum circa rectam lineam, (aut quidem circa quamvis
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            aliam) ſimiles innumeræ lineæ, vel figuræ parallelo juxta ſe ſitu
              <lb/>
            diſpoſitæ talit
              <unsure/>
            er conſtituuntur, ut ſingulæ centrum ſuum habeant in
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            dicta linea, quæ proinde tanquam axis rationem ſubit, ac talis deno-
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            minatur. </s>
            <s xml:id="echoid-s8866" xml:space="preserve">Quomodo, e. </s>
            <s xml:id="echoid-s8867" xml:space="preserve">c, in _cylindris obliquis_, ínque _conis Scalenis_
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            circuli circa lineam quandam rectam conſiſtunt; </s>
            <s xml:id="echoid-s8868" xml:space="preserve">quæ proptereà dicitur
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            ipſorum _axis_, quoniam in ea circulorum parallelorum _centra_ ex-
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            iſtunt. </s>
            <s xml:id="echoid-s8869" xml:space="preserve">Sed cùm motus ità diſtortos natura non capiat (ſaltem juxta
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            modum operandi ſimplicem quem nunc ſupponimus) & </s>
            <s xml:id="echoid-s8870" xml:space="preserve">quia poſſunt
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            hujuſmodi magnitudines ut modis aliis genitæ faciliùs concipi, de iis
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            abſtinebimus. </s>
            <s xml:id="echoid-s8871" xml:space="preserve">Neque non de magnitudinum per motus ſimplices
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            effectione ſufficiet hactenus diſſeruiſſe.</s>
            <s xml:id="echoid-s8872" xml:space="preserve">‖</s>
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