A Treatise on Mathematical Instruments: Including Most of the Instruments Employed in Drawing, for Assisting the Vision, in Surveying and Levelling, in Practical Astronomy, and for Measuring the Angles of Crystals...John Weale, 1849 - 183 σελίδες |
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Σελίδα 101
... bubble of air , bb , which rises to the highest part of the tube , so as to have its two ends equally distant from the middle , when the instrument is in adjustment , as represented in the annexed figure . The tube is generally fitted ...
... bubble of air , bb , which rises to the highest part of the tube , so as to have its two ends equally distant from the middle , when the instrument is in adjustment , as represented in the annexed figure . The tube is generally fitted ...
Σελίδα 102
... bubble will indicate quantities sufficiently minute , while those quantities correspond exactly to the changes of inclination , as read on the graduated limb of the instrument of which it forms a part . 66 Thirdly , the bubble must keep ...
... bubble will indicate quantities sufficiently minute , while those quantities correspond exactly to the changes of inclination , as read on the graduated limb of the instrument of which it forms a part . 66 Thirdly , the bubble must keep ...
Σελίδα 103
... bubble is standing at , counted from the fixed zero marks , at the instant of finishing an observation , must always be noted , that an allowance may be made for the value of the deviation in seconds , or as the case may re- quire . 66 ...
... bubble is standing at , counted from the fixed zero marks , at the instant of finishing an observation , must always be noted , that an allowance may be made for the value of the deviation in seconds , or as the case may re- quire . 66 ...
Σελίδα 106
... the first to adjust the bubble tube , so that it may truly indicate when the axis of the telescope is horizontal ; and the second to set the axis of the telescope perpendicular to the vertical axis round 106 MATHEMATICAL INSTRUMENTS .
... the first to adjust the bubble tube , so that it may truly indicate when the axis of the telescope is horizontal ; and the second to set the axis of the telescope perpendicular to the vertical axis round 106 MATHEMATICAL INSTRUMENTS .
Σελίδα 107
... bubble to the center of its run . Now reverse the telescope carefully in the Ys , that is , turn it end for end ; and , should the bubble not settle at the same point of the tube as before , it shows that the bubble - tube is out of ...
... bubble to the center of its run . Now reverse the telescope carefully in the Ys , that is , turn it end for end ; and , should the bubble not settle at the same point of the tube as before , it shows that the bubble - tube is out of ...
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Συχνά εμφανιζόμενοι όροι και φράσεις
accuracy adjustment altitude Architect's Scale axis azimuth beam compasses bisected breadth bubble called chain chromatic dispersion clamp coincide colatitude compasses construction correction cross wires described diaphragm distinct vision Ditto ditto divided drawing edge error extent will reach eye-piece feet figure focal length given number Gunter's chain half horizontal inches index glass instru instrument latitude lens lenses limb line of chords line of collimation line of numbers line of sines logarithmic marked means measured ment meridian microscope number of degrees object object-glass observed paper parallax parallel plate perpendicular placed plane position primary divisions prism protractor quarter girt radius rays reading reflected image reflector refracting Refracting Telescope represent right ascension round screw secants sector sextant side slider sliding speculum spirit level square station strument subdivisions tangents telescope theodolite tion transverse distance tube turning vernier plate vernier scale vertical circle zero
Δημοφιλή αποσπάσματα
Σελίδα 72 - ... that the sine of the angle of refraction bears a constant ratio to the sine of the angle of incidence...
Σελίδα 104 - In looking through a telescope a considerable field of view is embraced ; but the measurements indicated by any instrument, of which the telescope may form a part, will only have reference to one particular point in this field of view, which particular point is considered as the centre of this field of view. We must therefore place some fixed point...
Σελίδα 78 - When you have proved that the three angles of every triangle are equal to two right angles...
Σελίδα 107 - ... is out of adjustment, and requires correcting. The end to which the bubble retires must then be noticed, and the bubble made to return one-half the distance by turning the parallel plate screws, and the other half by turning the capstan-headed screw at the end of the bubble tube. The telescope must now again be reversed, and the operation...
Σελίδα 110 - The best constructed levelling staff* consists of three parts, which pack together for carriage in a neat manner, and, when opened out for use, form a staff seventeen feet long, jointed together something after the manner of a fishing-rod. The whole length is divided into hundredths of a foot, alternately coloured black and white, and occupying half the breadth of the staff; but for distinctness the lines denoting tenths of feet are continued the whole breadth, every half foot or five-tenths being...
Σελίδα 178 - Place the crystal which is to be measured on the table, resting on one of the two planes whose inclination is required, and with the edge at which those planes meet, nearest and parallel to the window.
Σελίδα 131 - Adjustments of the telescope : viz., the adjustment for parallax. for collimation. 2. Adjustment of the horizontal limb : viz., to set the levels on the horizontal limb to indicate the verticality of the azimuthal axis.
Σελίδα 179 - Now turn the graduated circle, by means of the handle, b, until the image of the bar, reflected from the second plane, is also observed to coincide with the same line below. In this state of the instrument the vernier at c will indicate the degrees and minutes at which the two planes are inclined to each other. " The accuracy of the measurements taken with this instrument will depend upon the precision with which the image cf the bar, reflected successively from both planes, is made to appear to...
Σελίδα 157 - Repeat the operation till the bubble retains the same position in both positions of the level, and the axis will be horizontal. To adjust the Line of Collimation in Azimuth. — Direct the telescope to some distant, small, and well-defined object, and bisect it by one extremity of the middle vertical wire, giving the telescope the azimuthal motion necessary for this purpose by turning the screw S. By elevating or depressing the telescope, examine whether the object is bisected by every part of the...
Σελίδα 99 - ... all his arrows. Ten chains, or 1000 links, have now been measured, and, this measurement having been noted in the field book, the follower returns the ten arrows to the leader, and the same operations are repeated. When the leader arrives at the end of the line, the number of arrows in the...