A Treatise on Mathematical Instruments ...1849 |
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Σελίδα 51
... object to be attained , in the use of this instrument , is the nice adjustment of the points G , H , to any definite distance apart . This is ac- complished by two vernier * , or reading plates b , c , each fixed . at the side of an ...
... object to be attained , in the use of this instrument , is the nice adjustment of the points G , H , to any definite distance apart . This is ac- complished by two vernier * , or reading plates b , c , each fixed . at the side of an ...
Σελίδα 54
... object were to enlarge the drawing to double its scale , then the tracer must be placed upon the arm DF , and the pencil at c ; and , if a copy were required of the same scale as the original , then , the sliding indices still remaining ...
... object were to enlarge the drawing to double its scale , then the tracer must be placed upon the arm DF , and the pencil at c ; and , if a copy were required of the same scale as the original , then , the sliding indices still remaining ...
Σελίδα 70
... object will be to consider the construction , and principles of action , of such instruments as are indispensable to assist the vision in making observations upon distant objects , whether upon terrestrial objects for the purposes of ...
... object will be to consider the construction , and principles of action , of such instruments as are indispensable to assist the vision in making observations upon distant objects , whether upon terrestrial objects for the purposes of ...
Σελίδα 71
... object is seen through it , be in a plane perpendicular to the edge of the prism ; and the axis of the pencil during ... object is viewed through a prism , the two following effects are produced . 1stly . The apparent position of the ...
... object is seen through it , be in a plane perpendicular to the edge of the prism ; and the axis of the pencil during ... object is viewed through a prism , the two following effects are produced . 1stly . The apparent position of the ...
Σελίδα 72
... object is observed , in order to make the apparent place of this object , as viewed through the prism , coincide with the actual place of other objects seen directly , as in the prismatic compass † , or for the mere pur- pose of ...
... object is observed , in order to make the apparent place of this object , as viewed through the prism , coincide with the actual place of other objects seen directly , as in the prismatic compass † , or for the mere pur- pose of ...
Άλλες εκδόσεις - Προβολή όλων
Treatise on Mathematical Instruments: Their Construction, Adjustment ... John Fry Heather Δεν υπάρχει διαθέσιμη προεπισκόπηση - 2016 |
Συχνά εμφανιζόμενοι όροι και φράσεις
accuracy achromatic adjustment altitude axis azimuth backwards beam compasses bisected breadth bubble called chromatic dispersion circle coincide colatitude collimation construction copy cosec cross wires cubic feet described diagonal divided drawing edge error extent will reach eye-piece figure focal length given line given number glass gnomonic projection horizontal hypothenuse inches instru instrument latitude lens lenses limb line of chords Line of Logarithmic line of numbers line of sines marked means measure meridian number of degrees object object-glass observed paper parallel pencil perpendicular plane position primary divisions prism proportional protractor quadrant quarter girt rays reading reflector represent right ascension right lines round scale of equal screw secants sextant side slider sliding speculum spirit level square straight edge straight lines stroke subdivisions taken tangents telescope theodolite tion tracing point transverse distance triangle tube turning vernier scale vertical
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 center of this field of view.
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 152 - The advantages of this instrument, when compared with the sextant, are chiefly these : the observations for finding the index error are rendered useless, all knowledge of that being put out of the question, by observing both forwards and backwards. By the same means the errors of the dark glasses are also corrected ; for if they increase the angle one way, they must diminish it the other way by the same quantity. This also perfectly corrects the errors of the horizon glass, and those of the index...
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 138 - Then press downwards the branches ee, which will cause the points to make punctures in the paper at opposite sides of the circle ; which being afterwards connected, the line will pass through the given angular point, if the instrument was first correctly set. In this manner, at one setting of the instrument, a great number of angles may be laid off from the same point. It is not essential that the centre be over the given point, when applied to...
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 153 - ... right, when, by a sweep of the index, the reflected image of any object will pass exactly over, or cover the image of that object seen directly. The third adjustment is, for making the line of collimation parallel to the plane of the circle. This is performed by two small screws, which also fasten the collar into which the telescope screws to the upright stem on which it is mounted: this is known to be right, when the sun and moon, having a distance of one...