WHEN 1975

WHAT DOES IT DO? Provides very precise measurements of position, including altitude, anywhere on Earth.

HOW DOES IT WORK? Signals are received from several Earth orbiting satellites. The computer calculates the position using this information.

Source: Department of Energy, Mines, and Resources.

Miller's Photoalidade

WHEN ca 1940

WHAT DOES IT DO? Measures angles in photographic surveys.

HOW DOES IT WORK? A pointer is lined up with a feature on the photo. The horizontal and vertical angles are indicated on the scales.

Source: Department of Energy, Mines and Resources

Builder's Levels

WHEN 15th -17th century 18^th century

WHAT DOES IT DO? Used in construction to ensure two points are level.

HOW DOES IT WORK? The level is hooked to a string spanning two points. A plumb bob is then hung from the level

Plumb Bobs

WHEN possibly 14^th to 15^th century 18^th century

WHAT DOES IT DO? Ensure objects are perfectly vertical.

HOW DOES IT WORK? The bobs hang from a string. Gravity ensures they hang straight down. Plumb bobs have been used in surveying and building since Egyptian times and maybe earlier.

Plane Table Alidade

WHEN Before 1906

WHAT DOES IT DO? Measures vertical angles.

HOW DOES IT WORK? This level sits on a plane table which is adjusted to the horizontal using the bubble. An object is sighted through the level and the vertical angle is read off the scale.

Reflecting Circle

WHEN ca 1880

WHAT DOES IT DO? Measures horizontal angles for marine navigation or surveys of coastlines.

HOW DOES IT WORK? Sighting are made through prisms to align two objects. Reading the angle with two verniers gives greater precision.

Gregorian Reflecting Telescope

WHEN ca 1736 to 1748

WHAT DOES IT DO? Magnifies astronomical objects for study.

HOW DOES IT WORK? Two concave mirrors are used to magnify objects. It produced better images than refracting telescope (which use lenses).

Transit Telescope and Riefler Clock

WHEN
Transit: ca 1880
Clock: ca 1904

WHAT DOES IT DO?
Beginning in 1905, this Riefler clock and a transit telescope provided the exact time for the Maritime provinces of Canada. These instruments provided standard time for railway stations, government buildings and mariners in Saint John and Halifax. Since the Earth rotates at a fairly constant speed, the time when certain stars were seen through the transit telescope was known. The Earth's motion served as the final reference and it was used to regulate the clock.

Source: Transit: Dominion Observatory; Clock: unknown

Split Lens Micrometer

WHEN ca 1880

WHAT DOES IT DO? Makes distance measurements at sea or on land.

HOW DOES IT WORK? A dial is rotated until two images seen through a split lens come together. Distance is calculated according to the reading on the dial.

Source: National Research Council of Canada, Archives

Engineers Chain

WHEN early 20^th century

WHAT DOES IT DO? Measures distances on land.

HOW DOES IT WORK? The surveyor and assistant pull the chain tight, then count the "tellers" or "combs" (10ft marks) and links (1ft marks).

Source: Department of Energy, Mines and Resources, Surveys and Mapping Branch

Sector

WHEN ca 1790

WHAT DOES IT DO? Used to measure and do calculations.

HOW DOES IT WORK? Sectors were made with scales suited to different trades. Scales are based on lengths and angles, as well as logarithmic and trigonometric functions.

For more information on our scientific instruments, contact the Curator, Physical Sciences and Medicine, David Pantalony.

Go back to Sampler of Scientific Instruments