Images(2)

Marvin sunshine recorder

Date1890-1910

Inventory Number1998-1-0837a,b

ClassificationSunshine recorder

Subject

Supplier Julien P. Friez 1852 - 1916

User Blue Hill Meteorological Observatory 1885-present

Cultural Region

Place of Origin

Place of Use

Dimensions22.2 x 27 x 8.3 cm (8 3/4 x 10 5/8 x 3 1/4 in.)

Material

Accessoriespart (a) is the stand, part (b) is the sensor

DescriptionThe device consists of a cylindrical glass tube with tips at both ends, which contains inside a thinner tube with bulbs at both ends. While one of the bulbs is transparent and cylindrical, the other one has been tinted black and has the shape of a cylinder with a sphere at its outer end. This inner tube is filled with air but also contains some mercury. At the midpoint between both of the bulbs, there are two electrical contacts that enter the tube. This is also the point where a brass clamp holds the outer tube, connecting the contacts in the device to two binding posts, one on the clamp, the other on the stand, that holds it. This clamp is held by the pivoting arm of a brass stand.

All the brass parts of this instrument are considerably rusted giving it a black-greenish color.

Signedon circular mark: JULIEN FRIEZ BALTIMORE BMD USA BEFORE OBSERVATORY

FunctionThis is the detector of a device that registers the times that the sun has been shining over an interval of time. It functions as an interruptor which closes a circuit when the amount of heat coming from sunshine is above a certain threshold. During its use, it would be connected by a cable to a recording instrument (which could be kept indoors or protected from the elements).

Following is a detailed description from the Glossary of Meteorology, published by the American Meteorological Society [Second Edition, 2000], and available online "http://amsglossary.allenpress.com/glossary" target="_blank">here:

"[The Marvin sunshine recorder] consists of two bulbs, one of which is blackened, that communicate through a glass tube of small diameter. The tube is partially filled with mercury and contains two electrical contacts. When the instrument is exposed to sunshine, the air in the blackened bulb is warmed more than that in the clear bulb. The warmed air expands and forces the mercury through the connecting tube to a point where the electrical contacts are shorted by the mercury. This completes the electrical circuit to the pen on the chronograph. The Marvin sunshine recorder is equally sensitive to the direct rays of the sun and to diffuse radiation from the sky (the heat from the latter at midday in overcast may be more than that from direct sunshine in the early morning); thus, the instrument is not without ambiguities. It is standard equipment at National Weather Service stations."

ProvenanceFrom the Blue Hill Meteorological Observatory in Milton, MA.