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 114
... perfect adjustment , and , when the image of the eye is brought upon the thread , all points bi- sected by the thread , whether seen by reflection , or directly through the opening , o , will be on the same level with the eye of the ...
... perfect adjustment , and , when the image of the eye is brought upon the thread , all points bi- sected by the thread , whether seen by reflection , or directly through the opening , o , will be on the same level with the eye of the ...
Page 118
... perfect adjustment , and any object be viewed by it after reflection at both the mirrors , the reading of the instrument gives the total deviation of the rays of light , by which the vision is produced , or the angle between the bearing ...
... perfect adjustment , and any object be viewed by it after reflection at both the mirrors , the reading of the instrument gives the total deviation of the rays of light , by which the vision is produced , or the angle between the bearing ...
Page 119
... perfect adjustment , place the dark glass before the eye - end of the telescope , and looking at the sun , and moving the index backwards and forwards a little distance on either side of zero , the sun's reflected image will be seen to ...
... perfect adjustment , place the dark glass before the eye - end of the telescope , and looking at the sun , and moving the index backwards and forwards a little distance on either side of zero , the sun's reflected image will be seen to ...
Page 120
... perfect adjustment ; but , if not , half the difference of the two readings is the amount of the error , and is called the index error , being a constant error , for all angles observed by the instrument , of excess , if the first ...
... perfect adjustment ; but , if not , half the difference of the two readings is the amount of the error , and is called the index error , being a constant error , for all angles observed by the instrument , of excess , if the first ...
Page 126
... perfect adjustment . The second telescope , placed beneath the horizontal limb , serves to detect any accidental derangement of the instrument during an observation , by noting whether it is directed to the same point of a distant ...
... perfect adjustment . The second telescope , placed beneath the horizontal limb , serves to detect any accidental derangement of the instrument during an observation , by noting whether it is directed to the same point of a distant ...
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...
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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...
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