A drosometer (from

Classical Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

, ''drosos'', dew + , ''metron'', measure) is an apparatus for measuring the quantity of

dew Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at whi ...

formed in a unit of time per unit area of surface.

Description

The surface may be either a horizontal metal plate or a leaf hanging naturally, or a bit of

wool Wool is the textile fibre obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have properties similar to animal wool. As ...

cotton Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor perce ...

representing a large surface of fine fibres. The unit of time is usually one hour, and the measurement is made in the early morning, before the rising sun evaporates the dew. When the apparatus is made self-registering, the surface, with its accumulating dew, hangs at one end of a delicate balance, or from a delicate spiral metallic spring, and by its gradual sinking moves the index that makes the record on a moving sheet of paper.

Shortcomings

Although many forms have been suggested, yet none have been considered to give results that are comparable with each other from day to day, owing largely to the fact that the slightest change in the surface that receives the moisture alters the quantity of dew that is caught. Even the same bit of wool, when used day after day, changes its nature in this respect. If a metallic surface is used, its behavior must be compared frequently with a standard, partly because different metals have different properties, but principally because the same surface, when it becomes greasy, dirty, or scratched, has different properties. Many peculiarities of the deposition of dew on different objects are explained in detail in the popular work by

Charles Tomlinson Alfred Charles Tomlinson, CBE (8 January 1927 – 22 August 2015) was an English poet, translator, academic, and illustrator. He was born in Penkhull, and grew up in Basford, Stoke-on-Trent, Staffordshire. Life After attending Longton High Sc ...

, entitled ''The Dew-drop and the Mist'' (London, 1860). Moreover, the case of the natural deposition of dew on the grass and other plants very near the surface of the ground is not at all parallel to that where it is deposited upon metal plates or other bodies used as drosometers, partly because of the location, partly because of the difference in the substances, and largely because of the influence of slight local currents of air.

References

*{{Cite NIE, wstitle=Drosometer, year=1905 Meteorological instrumentation and equipment