cloud plotter
Date1890
Inventory Number1998-1-0835
ClassificationMeteorology
Subject
Maker
Henry Helm Clayton
1861 - 1946
Maker
Sterling P. Fergusson
1868 - 1959
User
Blue Hill Meteorological Observatory
1885-present
Cultural Region
Place of Use
Dimensions14.5 × 36 × 17.4 cm (5 11/16 × 14 3/16 × 6 7/8 in.)
Material
Accessoriestwo thin metal rods (one with a sliding disk attached); metal pin with a hole
DescriptionThis device consists of a rectangular metal base with levelling screws, on which two miniature models of theodolites are mounted. The distance between the two theodolites can be altered.
Each of the theodolites can be made to point to a specific orientation in space (azimuth and altitude) for which they have corresponding scales.
The entire plotting set-up used with this instrument consisted, in addition to this instrument, of several stands used to support threads that would extend from each of the theodolites in their direction of sight. The threads from each of the theodolites were meant to intersect at a point above the instrument that represented the position of a cloud. Tension for the threads would have been provided by a plumb, which extended the threads vertically from the intersection of the two lines of sight to the surface on which the plotter rested. On this surface a coordinate grid would had been laid. The plumb thus indicated the geographical coordinates of the cloud.
Each of the theodolites can be made to point to a specific orientation in space (azimuth and altitude) for which they have corresponding scales.
The entire plotting set-up used with this instrument consisted, in addition to this instrument, of several stands used to support threads that would extend from each of the theodolites in their direction of sight. The threads from each of the theodolites were meant to intersect at a point above the instrument that represented the position of a cloud. Tension for the threads would have been provided by a plumb, which extended the threads vertically from the intersection of the two lines of sight to the surface on which the plotter rested. On this surface a coordinate grid would had been laid. The plumb thus indicated the geographical coordinates of the cloud.
Signedengraved in base: No 135 / L.GOLAZ ET FILS CONST'rs / 24, rue des Fossés St Jacques / PARIS 1884
FunctionThis is a plotting machine for determining the position of clouds by triangulation.
The two miniature theodolites are meant to represent actual theodolites that had been used for observations at a distance of several miles from each other. The actual theodolites would have been used to pinpoint the location of clouds. Readings would have been made from two locations simultaneously.
Once the readings were available, this plotter was used to determine the position of the clouds that had been sighted. This was a visual alternative to calculating the coordinates analytically.
The two small thodolites would have been aligned to the proportional height, latitude and longitude of the locations where the actual theodolites had taken their readings. Then, threads (supported from stands) from each small theodolite were set up along their line of sight. The position of the cloud would be at the intersection of the threads coming from each theodolite. From this point of intersection, the treads would stretched directly downwards with the help of a plumb, almost to reach the surface on which the plotter was located. If a map or coordinate grid was placed on the surface, the plumb would point to the coordinates of the cloud.
Successive readings of the same cloud would allow velocity determination.
A photograph of this instrument set up for operation over a map with threads supported by stands can be seen in: John H. Conver, The Blue Hill Meteorological Observatory: The First 100 Years - 1885-1985 , 1990, pg 51, fig 24.
The two miniature theodolites are meant to represent actual theodolites that had been used for observations at a distance of several miles from each other. The actual theodolites would have been used to pinpoint the location of clouds. Readings would have been made from two locations simultaneously.
Once the readings were available, this plotter was used to determine the position of the clouds that had been sighted. This was a visual alternative to calculating the coordinates analytically.
The two small thodolites would have been aligned to the proportional height, latitude and longitude of the locations where the actual theodolites had taken their readings. Then, threads (supported from stands) from each small theodolite were set up along their line of sight. The position of the cloud would be at the intersection of the threads coming from each theodolite. From this point of intersection, the treads would stretched directly downwards with the help of a plumb, almost to reach the surface on which the plotter was located. If a map or coordinate grid was placed on the surface, the plumb would point to the coordinates of the cloud.
Successive readings of the same cloud would allow velocity determination.
A photograph of this instrument set up for operation over a map with threads supported by stands can be seen in: John H. Conver, The Blue Hill Meteorological Observatory: The First 100 Years - 1885-1985 , 1990, pg 51, fig 24.
W. & L. E. Gurley
Date: ca. 1884
Accessories: solar attachment; case; level; green filter; sun shade; tripod (5163b)
Object number: 5163a
Buff & Buff Manufacturing Company
Date: circa 1905
Accessories: wood case; leather case; right-angle prism; plumb bob; oil flask; tripod (5174b)
Object number: 5174a
Andrew Yeates
Date: circa 1840
Accessories: case, second eyepiece, plumb bob
Object number: 5235
Benjamin Cole
Date: 1720-1740
Accessories: sight vane (2), key (box)
Object number: 5253
