Volume 1

The sector on a quadrant, or, a treatise containing the description and use of four several quadrants; two small ones and two great ones, each rendred many wayes, both general and particular. Each of them accomodated for dyalling; for the resolving of all proportions instrumentally; and for the ready finding the hour and azimuth universally in the equal limbe. Of great use to seamen and practioners in the mathematicks / Written by John Collins accountant philomath. Also an appendix touching reflected dyalling [by J. Lyon] From a glass placed at any reclination.

  • Collins, John, 1625-1683.
Date:
1659
Catalogue details

Licence: Public Domain Mark

Credit: The sector on a quadrant, or, a treatise containing the description and use of four several quadrants; two small ones and two great ones, each rendred many wayes, both general and particular. Each of them accomodated for dyalling; for the resolving of all proportions instrumentally; and for the ready finding the hour and azimuth universally in the equal limbe. Of great use to seamen and practioners in the mathematicks / Written by John Collins accountant philomath. Also an appendix touching reflected dyalling [by J. Lyon] From a glass placed at any reclination. Source: Wellcome Collection.

    395/412 (page 15)
    Reflected Diallingfroi» 4n]f Recihing Glafc* i y • that the thread and plummet may hang without; the room: then by help of the Suns Azimuth you may draw the meridian line, (as before) as if the GlalTe were horizontal, and move the lath wiih the thread and plummet at the end of it to and ft o, until the thread and plummet be in the diredl meridian of the woild with the center of the Glade. Then (as before) tie a thread erode the room, in fuch fort that from or by fome part of ?he faid thread both tjie Reclining glalfeand the thread to which the plummet is faftenjbd may be feen at one time* -Then (as before) on the laid thread, which crofTes the room, I tie a (lipping knot? which I move to and fro on the faid (iringj until by looking in the faid Glaffe I find from my eye the faid knot and fome part of the per- pendieularthread without, alias it were in one right line? the one fhadowing or interpofing the fight of the other, being then very careful to keep that knot in the fame poiition, then take the thread (whofe end whereof being fafiened in the faid center of the Glaife) and bringing it juft totouch the faid knot, I augment that thread, until the end thereof touch the faid wall or Cieling, and the faid thread alfo touch the knot, as before .* then in place where the end of the faid thread toucheih the wall or Cic- lin<^, I make a mark, which mark or point will be dire6lly in the reffedled meridian of the world, according to the fituation of that Glaflc. Then again I remove that thread (overthwart tke room) on which the faid knot is, either higher or lower then it formerly was at pleafurc, ftiU having regard that from fome part 01 the laid thread within, you may fee both the Reclining Glafle, and the perpendicular thread without at one time; and (asbefore) move the faid flipping knot on the faid thread, until by looking in the faid Reclining Glaffc, you fee the faid knot and fome part perpendicular thread without in one right line, fo as the one ha- dows or hinders the fight of the other, (as before) which knot then rauft not be removed from its fituation, then take that threa fwhofe end is fattened in theGlaffe) and bring it to touch that Lot, the end of the faid thread being continued to touch the wall or Cieling: fo is that point of touch on the Cieling another L point