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 10
... feet , & c .; if the subdivisions are taken as tens , the primary divisions will be hundreds ; and , if the primary divisions be units , the subdivisions will be tenths . The accompanying drawing represents six of the simply divided ...
... feet , & c .; if the subdivisions are taken as tens , the primary divisions will be hundreds ; and , if the primary divisions be units , the subdivisions will be tenths . The accompanying drawing represents six of the simply divided ...
Σελίδα 11
... feet and inches , 6 feet 7 inches for instance , extend the compasses from the primary division numbered 6 , to the 7th upper subdivision , reckoning backwards , as before . Diagonal Scales . - In the simply divided scales one of the ...
... feet and inches , 6 feet 7 inches for instance , extend the compasses from the primary division numbered 6 , to the 7th upper subdivision , reckoning backwards , as before . Diagonal Scales . - In the simply divided scales one of the ...
Σελίδα 31
... feet long by 15 inches broad . Extend from 1 to 1.25 , for 15 inches equals 1.25 feet , and this extent will reach from 27 feet to 33.75 feet , the super- ficial content required . Second Method . - Extend from 12 to the number of ...
... feet long by 15 inches broad . Extend from 1 to 1.25 , for 15 inches equals 1.25 feet , and this extent will reach from 27 feet to 33.75 feet , the super- ficial content required . Second Method . - Extend from 12 to the number of ...
Σελίδα 32
... feet 9 inches long ? The extent from 1 to 1.25 reaches forward from 1.25 to 1.56 , the superficial content of a section of the pillar ; and the ex- tent from 1 to 1.56 reaches from 21.75 to 34 , or more accu- rately to 33.93 , the solid ...
... feet 9 inches long ? The extent from 1 to 1.25 reaches forward from 1.25 to 1.56 , the superficial content of a section of the pillar ; and the ex- tent from 1 to 1.56 reaches from 21.75 to 34 , or more accu- rately to 33.93 , the solid ...
Σελίδα 40
... Feet and Inches in such a manner that an extent of Three Inches shall represent Twenty Inches.- 1. Make three inches a transverse distance between 10 and 10 , and the transverse distance of 8 and 8 will represent 16 inches . 2. Set off ...
... Feet and Inches in such a manner that an extent of Three Inches shall represent Twenty Inches.- 1. Make three inches a transverse distance between 10 and 10 , and the transverse distance of 8 and 8 will represent 16 inches . 2. Set off ...
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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...