The Compass.$A monthly journal for engineers, surveyors, architects, draughtsmen, and student ..., Volumes 1-3Keuffel & Esser Company, 1891 |
Common terms and phrases
127 Fulton Street accuracy adjustment altitude angle of incidence ascertained attached axis bubble centre circle Clinometer coincide COMPASS corresponding curve degrees diameter disc divisions drawing equal error feet figure foot formula German silver give given gradienter graduated height Heliograph horizontal distance horizontal line HOUR ANGLE intersection Journal for Engineers KEUFFEL & ESSER length lens limb logarithmic logarithmic scale means measured method Metres metric system millimetres minutes mirror Monthly Journal needle object obtained optical axis ordinary Pantograph paper parallax parallel perpendicular plane Planimeter plate plumb-bob position prism protractor radius ratio rays of light reading refraction revolve scale screws series of numbers Sextant shown in Fig side sine Slide Rule slope solar spirit level surface Surveying Instruments Surveyors tangent tape telescope tion transit transit telescope triangle tube vernier vertical whence WILLIAM COX York City zero ΙΟ
Popular passages
Page 22 - Four quantities are said to be proportional when thejatio of the first to the second is the same as the ratio of the third to the fourth.
Page 166 - When a ray of light passes from one medium to another, it is refracted so that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the velocities in the two media.
Page 76 - ... ago. Whenever a needle happened to be made of magnetic iron, it might reveal its quality by falling into a cup of water, when it happened to be attached to a splinter of wood, for example. It came in some such way to be known commonly that certain needles had this quality. The great producing centre for magnetic iron is Tszchou, in southern Chihli. This city was very early called the City of Mercy...
Page 77 - This variation went on increasing till a century later, that is, till the ninth century. A professor of geomancy then added a new circle to the compass. On this improved compass the first of the twelve hours begins on the new circle at 7$° east of north. The compass, it will be observed, grew out of the old astrological report or nativity paper, calculated from the position of the stars, and prepared in the Han dynasty by astrologers as a regular part of social life, especially when marriages were...
Page 74 - CB : CA : : sin A : sin B. For, with A as a centre, and AD equal to the less side...
Page 145 - In order to determine just what accuracy was possible with a Saegmuller Solar Attachment, I spent two days in making observations on a line whose azimuth had been determined by observations on two nights on Polaris at elongation, the instrument being reversed to eliminate errors of adjustment. Fortyfive observations were made with the solar attachment on Oct. 24, 1885, from 9 to 10 AM, and from 1.30 to 4 p.
Page 146 - He says:"This table is valuable in indicating the errors to which the work is liable at different hours of the day and for different latitudes; as well as serving to correct the observed bearings of lines when it afterwards appears that a wrong latitude or declination has been used. Thus, on the first day's observations I used a latitude in the forenoon of 38° 37', but when I came to make the meridian observation for latitude I found the instrument gave 38° 39'.
Page 147 - This was the latitude that should have been used, so I corrected the morning's observations for two minutes error in latitude by this table. " It is evident that if the instrument is out of adjustment, the latitude found by a meridian observation will be in error ; but if this observed latitude be used in setting off the co.latitude, the instrumental error is eliminated. Therefore always use for the co.latitude that given by the instrument itself in a meridian observation.
Page 76 - ... suppose it was in any way foreign, because the Chinese use an enormous number of needles, and have an inexhaustible supply of ironstone. But though the polarity was known, it was not turned to a practical use till the Tsin dynasty, when landscapes began to be studied by the professors of fengshui, or geomancy. There was at that time a general belief in the magical powers of natural objects. This was a Buddhist doctrine, and it took firm hold on the Chinese mind of that age. The Chinese philosophers...
Page 127 - ... and the optician could construct, and so enabled us to penetrate into mysteries hidden in stars apparently single, and altogether unsuspected of being binary systems. The spectroscope has not simply added to the list of the known binary stars, but has given to us for the first time a knowledge of a new class of stellar systems, in which the components are in some cases of nearly equal magnitude and in close proximity, and are revolving with velocities greatly exceeding the planetary velocities...