Selected quad for the lemma: end_n

Word A	Word B	Word C	Word D	Occurrence	Frequency Band	MI	MI Band	Prominent
end_n	east_n	point_n	west_n	1,970	5	9.4719	5	true

Text snippets containing the quad

ID	Title	Author	Corrected Date of Publication (TCP Date of Publication)	STC	Words	Pages
A44320	Lectiones Cutlerianæ, or, A collection of lectures, physical, mechanical, geographical, & astronomical made before the Royal Society on several occasions at Gresham Colledge : to which are added divers miscellaneous discourses / by Robert Hooke ...	Hooke, Robert, 1635-1703.	1679 (1679)	Wing H2617; ESTC R4280	276,083	420

the extent of two right ones For 't is plain enough that the two Tubes I first described apply'd to the Quadrant will measure any Angle to a Quadrant or right Angle and 't will be as easie to understand how by the help of the Reverse-Tube any Angle between a Quadrant and two right Angles may be measured To make this a little plainer to the Reader let c c c c c in the 12th Figure represent the under Tube or fixed Sight s the hole or Eye-cell t r a round piece carrying the reflex Mettal g g this is made to turn round and the reflecting Mettal g g being fixed to it within the Tube is carried round also with it Let s i k l m x represent the Ray passing forwards by the Eye-Glass Thread-Sight and Object-Glass then this round piece t r being turned and made r t as in the 13th Figure is represented and with it the reflecting Mettal g g here marked q q being turned also the Line s q k l m y will represent the Ray reflected and passing backwards by the reflex-Mettal q q Eye-Glass k Thread-Sight l and Object-Glass y. The measure of the Angle is found by the same Apparatus or Screw-Plate for as much as the Screw-Plate would shew the Angle less then a Quadrant if the fore-part of the Tube were used by so much is the Angle more then a Quadrant if the reverse or back part of the Tube be used and the same reason of the accurateness and certainty for the one is good for the other without being lyable to any manner of Objection or Inconvenience It remains therefore now only to shew First How these two Perspective or Telescope Sights placed within the same Tube may be made to look exactly forwards or backwards in the same Line And secondly How they shall be adjusted to the Telescope fixt upon the moveable arm of the Quadrant so as to know when the Division-Angle begins and when they are open'd to a Quadrant right Angle or 90 Degrees for unless these be ascertain'd and fixt to as great a measure of accurateness as the contrivance of the Screw is capable of dividing or the Telescope-Sights are capable of distinguishing or the Perpendicularity ascertain'd all the pains care industry and curiosity bestow'd about the other are of no use First then For fixing the Thread-Sights of the two Telescopes within the same Tube so as to look directly forward and backwards care must be taken that every one of the four Glasses that is to say the two Object-Glasses and the two Eye-Glasses must be so steadily and securely fixt into the Tube that they cannot by any means be stirr'd or removed the manner of doing which I suppose so exceeding easie that I need not spend time in describing a way to do it Next Sufficient care must be taken of the stiffness of the Tubes that they may not warp or bend Thirdly One of the Thread-Sights must be fixt as firmly and securely as the Glasses and so that the crossing of the Threads may be as near as possible in the Axis of the Object and Eye-Glass the other Thread-Sight must be left free till by several tryals it be found to stand exactly in the same Line with the first the manner of doing which I shall now describe There being two Threads which cross each other the one Perpendicular and the other Horizontal care must be taken that both these lye exactly in the same Lines with the Horizontal and Perpendicular Threads in the other Sights and in order thereunto there must be two Frames of Brass represented in the 29 and 30 Figures of the 2d Plate of the bigness of the hollow of the Tube these must have groves made in the Tube fit to receive them in which they may by the help of Screws be moved and made to slide to and fro as there is occasion for their adjusting Next They must lye so close together that the Hairs may touch each other And thirdly They must cross exactly in the Focus of the Object and Eye-Glass One of these Frames must carry the Perpendicular Thread and by a Screw in the side of the Tube must be moveable to the right or left side as there is occasion the other Frame must carry the Horizontal Thread and by a Screw in the top of the Tube must be made to rise or fall in the Tube as there is need The Mechanical Fabrick of which is so easie that I hope I need not spend time in the further Description thereof but refer the Reader to the 29 and 30 Figures These things being thus done from the top of some Turret or any other Station where two opposite places at a considerable distance as half a mile or a mile or two can be plainly seen find out two Points which at the first looking through your Glasses you find to be shewn out by the Crosses of the Thread-Sights then note those Points very diligently that you may be sure to find them and know them again when you have removed the Glasses this done turn the ends of the Tube and if you were looking Eastwards and Westwards turn that part towards the East which before looked Westwards and vice versâ and find out the two Points you saw in the former Observation then directing that part that hath the fixt Threads to the Point that was seen before by the moveable Threads find out the other Point which you will be sure to see within the compass of your Eye-Glass and observe how far the cross Threads are now removed from it either Northwards or Southwards upwards or downwards then as near as you can by your judgement half that Difference and by the Screws move the Frames that the Threads may stand in the middle between the two Points then take notice again of the Points shewn by the Threads and turn the Tube again Do this so many times till you find upon converting the Tubes that you see the same Points to be marked by the Crosses of the Thread-Sights with which end soever you look on them and then the Tube will be exact and fit for use The reason of this adjusting will be sufficiently plain to any one that shall consider the 14th Figure Where let v represent the middle of the Tube t u b or the place of the Eye and let w represent the Object seen Westwards and e the Object Eastwards at the first view then keeping the middle of the Tube exactly upon the same Point u turn the end of the Tube t towards the East and the end b towards the West and find out first the Eastern Object e and finding the other Cross to direct now to the Point p and not to w divide the Distance between the Point w and the Point p as exactly as you can in half which if you chance to hit exactly at first it will be the middle Point m but if you do not but you rectifie it only to r then by the