General Information

Serial #

N/A

Part Number

1

Total Parts

2

AKA

stillwell

Patents

N/A

General Description

brass

Dimensions

Note: These reflect the general size for storage and are not necessarily representative of the object's true dimensions.

Length

N/A

Width

N/A

Height

19.0 cm

Thickness

N/A

Weight

N/A

Diameter

20.2 cm

Volume

N/A

Lexicon

Group

Meteorology

Category

Evaporation amount measurement

Sub-Category

N/A

Manufacturer

AKA

Environment CA

Country

Unknown

State/Province

Unknown

City

Unknown

Context

Country

Canada

State/Province

Unknown

Period

at least 1961 to 1974; this instrument was apparently in use for 40 years (Ref. 6)

Canada

An example of a piece of equipment used for measuring evaporation by the Meteorological Service of Canada at observing sites across Canada. The Class A evaporation pan and fixed point gauge were being used by the MSC by 1961 (Ref.s 4-5) and until at least the mid 1970's (Refs. 2-3). Part of a large collection of meteorological instruments acquired from the Meteorological Service of Canada (previously Atmospheric Environment Service) by the CSTM since 1967. MSC is the government agency responsible for collecting and disseminating meteorological data and forecasts in Canada. It was founded in 1871 in Toronto where it is still headquartered. The MSC was originally on the University of Toronto downtown campus but moved to Downsview in 1971 on land owned by UofT. The headquarters houses laboratories, research facilities and calibration and instrument maintenance facilities (now largely contracted out).

Function

A device consisting of a pointed brass rod fixed in a stillwell (a cylindrical vessel), placed in a four foot diameter evaporation pan and used to measure the change in the level of the free water surface in the pan, in order to measure the rate of evaporation. The top of the pointed rod (the fixed point) served as a reference mark for the water level in the pan.

Technical

A MSC stilling well for the MSC evaporation pan. It was used with a 4' wide Class A evaporation pan (Ref. 1) . The Class A evaporation pan, which was recommended by the World Meteorological Organization as an interim reference standard, was used at observing stations in Canada to obtain an estimate of evaporation during the growing or frost-free season. It was not suitable for measuring evaporation from arid or semi-dry locations such as ripe wheat fields, but was useful for obtaining data from open water areas and from saturated soil and cropped areas under various conditions (Ref. 3) . The U.S also used a cylindrical above ground evaporation pan, 250 mm deep and 1.2 m in diameter, with a fixed point gauge, while the B.M.O. used a sunken square tank and a graduated rule (Ref. 6). The fixed point gauge consists of a pointed brass rod fixed in a four inch diameter container called a stillwell, which sits in an evaporation pan.. The latter has a small hole in its side near the base to allow a flow of water from the pan without passing on ripples or small disturbances. Ancillary equipment used with the evaporation pan and fixed point gauge included a graduate for adding measured amounts of water to the pan (see 1987.0877 for a non MSC? evaporation graduate); mounted MSC/AES maximum thermometers (see 1987.0689 -1978.0690) and minimum thermometers (see 1987.0694 -1978.0695) in the evaporation pan and in a Stevenson screen (see 1967.1201); a standard MSC rain gauge (see 1987.0598 etc.) and graduate (see 1987.0602); and a totalizing anemometer (2004.0350) (Refs. 2-3).

Area Notes

Unknown

Details

Markings

none visible

Missing

appears complete

Finish

obscured by corrosion

Decoration

N/A