Treatise on Mathematical Instruments: Their Construction, Adjustment, Testing and Use Concisely ExplainedVirtue Bros. & Company, 1866 - 185 pages |
From inside the book
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Page 82
... cross - wires or spider - lines at the place of the image in the field of view , for the purpose of accurately measuring the position of an object , at the time of observation , or to apply an apparatus , called a micrometer , for ...
... cross - wires or spider - lines at the place of the image in the field of view , for the purpose of accurately measuring the position of an object , at the time of observation , or to apply an apparatus , called a micrometer , for ...
Page 99
... cross wires will be situated on the prolongation of the horizontal line A o . Suppose now the position of the diaphragm carrying the cross wires to have become deranged . so that the point of inter- section is moved to B , then every ...
... cross wires will be situated on the prolongation of the horizontal line A o . Suppose now the position of the diaphragm carrying the cross wires to have become deranged . so that the point of inter- section is moved to B , then every ...
Page 100
... cross wires will be as much above the true level point on the line A o as the point before bisected by them was below it . The true level point is therefore midway between the two points observed in the two positions of the telescope ...
... cross wires will be as much above the true level point on the line A o as the point before bisected by them was below it . The true level point is therefore midway between the two points observed in the two positions of the telescope ...
Page 102
... cross wires . If this perfection in the construction of the in- strument does not exist , the line of collimation will vary , as the tube carrying the object - glass is thrust out , and drawn in , to adjust the focus for objects of ...
... cross wires . If this perfection in the construction of the in- strument does not exist , the line of collimation will vary , as the tube carrying the object - glass is thrust out , and drawn in , to adjust the focus for objects of ...
Page 126
... cross wires will move accurately along the angle of the building , still continuing in coincidence with it . A still more perfect test will be to make the intersection of the cross wires coincide with the reflected image of a star in an ...
... cross wires will move accurately along the angle of the building , still continuing in coincidence with it . A still more perfect test will be to make the intersection of the cross wires coincide with the reflected image of a star in an ...
Common terms and phrases
accuracy achromatic adjustment altitude axis azimuth beam compasses bisected breadth bubble called chromatic dispersion clamp coincide colatitude compasses construction correct cross wires described diaphragm distinct vision Ditto ditto divided drawing edge equal error extent will reach eye-piece feet figure fixed focal length given number goniometer graduated half horizontal inches index glass instru instrument intersection IVY LANE latitude lens lenses limb line of collimation line of numbers line of sines logarithmic means measured ment meridian microscope number of degrees object-glass observed paper parallax perpendicular placed plane position primary divisions prism protractor quarter girt radius rays reading reflected image reflector refracting refracting telescopes represent right angles right ascension round secants sector sextant side Slide Rule sliding speculum spherical aberration spirit level square staff station subdivisions tangents telescope theodolite transit transverse distance triangle tube turning vernier scale vertical circle zero
Popular passages
Page 5 - To which is added, a description of the Principles and Practice of Isometrical Projection. By JF HEATHER, MA -With 14 Plates.
Page 69 - ... that the sine of the angle of refraction bears a constant ratio to the sine of the angle of incidence...
Page 98 - ... of this field of view. We must therefore place some fixed point in the field, of view, and in the focus of the eye-piece, and the point to which the measurement will have reference will be that point of the object viewed, which...
Page 6 - Gd. 131. READY-RECKONER FOR MILLERS, FARMERS, AND MERCHANTS, showing the Value of any Quantity of Corn, with the Approximate Values of Mill-stones & Mill Work.
Page 11 - THE ENTIRE SERIES IS FREELY ILLUSTRATED ON WOOD AND STONE WHERE REQUISITE. The Public are respectfully informed that the whole of the late MB.
Page 5 - Gd. 55. NAVIGATION ; the Sailor's Sea Book : How to Keep the Log and Work it off, &c. ; Law of Storms, and Explanation of Terms, by J. Greenwood. 2s.
Page 24 - From the center at a draw the line ag for the axis of the gnomon agi, and from g let fall the perpendicular gi upon the horizontal meridian line an, and there will be formed a triangle ag i.
Page 143 - ... of them, those which apply to the eye-end of the telescope will answer much better ; the former having their errors magnified by the power of the telescope, will, in proportion to this power, and those errors, be less distinct than the latter. " In taking distances, when the position does not vary from the vertical above thirty or forty degrees, the handles which are attached to the circle are generally most conveniently used ; but in those which incline more to the horizontal, that handle which...
Page 3 - Denison. 3s. 6d. 78. STEAM AND LOCOMOTION, on the Principle of connecting Science with Practice, by J. Sewell. 2s. 78*.