King's College Road

King's College Road
Convocation Hall.

King's College Road
Sandford Fleming Building.

King's College Road
Sun dial, with University College in the background.

TORONTO TIME

THE GNOMON OF THIS SUNDIAL, BEING PARALLEL TO THE EARTH'S AXIS OF ROTATION, POINT TO THE NORTH CELESTIAL POLE. IT'S ANGLE ABOVE THE HORIZONTAL IS THUS 43°40' (THE LATITUDE OF TORONTO). THE SHADOW CAST ON THIS EQUATORIAL SCALE (ROMAN NUMERALS) SHOWS THE APPARENT SOLAR TIME FOR THIS LONGITUDE (79°24' WEST OF GREENWICH), XII (NOON) MARKING THE SUN'S CROSSING OF THE MERIDIAN.

THE NATURE OF THE EARTH'S MOTION CAUSES THE LENGTH OF THE SOLAR DAY TO VARY APPRECIABLY THROUGHOUT THE YEAR. TO YIELD TORONTO MEAN TIME THE SUNDIAL READING MUST BE ADJUSTED ACCORDINGLY. TO CONVERT IT TO EASTERN STANDARD TIME (MEAN TIME FOR THE 75TH MERIDIAN), 17½ MINUTES MORE MUST BE ADDED. THE TOTAL CORRECTION IS TABULATED ON THE SUNDIAL BASEPLATE.

THE SUN'S DECLINATION, ITS ANGULAR DISTANCE NORTH OR SOUTH OF THE CELESTIAL EQUATOR, IS SHOWN BY THE SHADOW OF THE CENTRAL BEAD (USING THE ARABIC NUMERAL SCALE, POSITIVE FOR NORTH). OWING TO THE TILT OF THE EARTH'S AXIS, THE VALUE VARIES UP TO 23½° IN EITHER DIRECTION, IN A SIMPLE ANNUAL CYCLE. THE SUN'S ELEVATION ABOVE THE SOUTHERN HORIZON AS IT CROSSES THE MERIDIAN IS FOUND BY ADDING 46°20' (THE CO-LATITUDE) THE DECLINATION.

King's College Road
The Meridian of Toronto.

THE MERIDIAN OF TORONTO

THIS LINE, IN THE TRUE NORTH-SOUTH DIRECTION THROUGH THE SITE OF THE TORONTO MAGNETIC OBSERVATORY, MARKS THE MERIDIAN FOR TORONTO THAT WAS RECOGNIZED BY SCIENTISTS AROUND THE WORLD UNTIL 1908.

EACH SECTION OF THIS BEAM IS 3.085 METRES LONG, EQUIVALENT TO 0.1 SECONDS OF ARC OF LATITUDE, EXMPLIFYING THE HIGH PRECISION OF THE 1883 DETERMINATION OF THE LATITUDE AND LONGITUDE OF THE OBSERVATORY, RECORDED ON THE TRANSIT PILLAR NEARBY.

IN 1840, MAGNETIC NORTH HERE WAS ALMOST COINCIDENT WITH TRUE NORTH, BUT HAS DRIFTED SLOWLY WESTWARD SINCE THAT TIME. BY 1898, WHEN MAGNETIC OBSERVATIONS HAD TO BE ABANDONED AT THIS SITE OWING TO INTERFERENCE FROM THE NEWLY ELECTIRFIED STREET RAILWAYS, THE VARIATION HAD REACHED 5 DEGREES.

King's College Road
People relaxing on the steps of the Medical Sciences Building.