Jules-Louis Gabriel Violle, French physicist (1841-1923).
Two bulbs, consisting o thin sheet cooper, one in dull black on the outside, the other polished and gilt. Both bulbs are jet black internally. Each carries a thermometer divided in 1/5 Celcius.

Functioning:
Used for measuring the thermal radiation of the sun.

This instrument was made in Russia.

"Keilsichtmesser nach Prof. Dr Wigand"
Dr A. Wigand developed in the 1910ies a method for measuring the transparency of the atmosphere. The instrument comprises a prism with varying density.
Serial No 100762

Aneroid Barograph.
Uses a small, flexible metal box called "aneroid cell" which is sealed after some of the air is removed, so that small changes in external air pressure cause the cell to expand or contract.
The registering aneroid barograph consists of a revolving drum on which the air pressure is recorded, a syphon cell that expands or contracts as air pressure rises and falls, and a lever that transfers the movement of the syphon cell to the recording pen that writes on the revolving drum.

In the Fortin barometer, the level of mercury in the glass at the bottom of the barometer cistern is adjusted to a scale zero, known as the fiducial point, each time a reading is to be taken. The level of mercury in the column is then read against the scale, using a vernier adjustment for extra accuracy.
The Observatory bought 11 barometers of this type in 1899 in order to equip the Greek meteorological stations.

Aspiration psychrometer conceived by the meteorologist Richard Assmann in 1892.

Psychrometers are measuring instruments designed
to determine the relative humidity of the
atmosphere in the vicinity of the instrument.
The humidity value is calculated from the
temperature difference (psychrometric difference)
between two different thermometers.
The first thermometer measures the dry ambient
temperature, the second thermometer measures the
temperature of a moistened thermometer. Through
the evaporation of water, evaporation heat is drawn

The instrument masures evaporation. 1mm on the scale means that 25g of water evaporated.

The Radiometer has been compared with the Eppley scale of reference standards. The derived value of the constant for these instrumentsv is 8.37 Milivolt/cal cv min-1 (int)

Serial No D7860

Zu diesem Apparat gehört Schreibstreifen R. Fuess Nr 157m

Dr Stephens Windrichtungs Indikator

This wind indicator receives electric signals from the weathercock