392 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
instruments, for which certificates from Kew Observatory have been 
obtained. 
The Shade Temperature Thermometers, — The thermometers for deter^ 
mining the temperatm^e of the air in shade are suspended in a Steven- 
son thermometer screen of the Royal Meteorological Society's pattern. 
They consist of a maximum thermometer on the Negretti principle, which 
registers the greatest heat during the daytime, and a Rutherford spirit 
minimum thermometer for showing the lowest reading at night. There 
is also a dry and a wet bulb thermometer, which jointly give the humidity 
of the air, while the dry bulb is further available as giving the actual 
temperature at any time. 
The Exposed Thermometer. — This is a very sensitive minimum ther- 
FiG. 139. — Meteorological Station at Chiswick. 
mometer which rests horizontally on short grass and registers each night 
the greatest cold experienced by low-growing vegetation. When the 
ground is covered with snow this thermometer is placed lightly on the 
surface of the snow covering. 
Soil Te^nperatures. — These are obtained by means of three Symons's 
earth thermometers, the bulbs of which are respectively 1 foot, 2 feet, 
and 4 feet beneath the surface of the grass covering the instrument 
enclosure. These earth thermometers show the temperature to which 
the roots of plants at the depths named are at any time exposed. 
The Bain- Gauge. —Thi?, is a stout 8-inch copper rain-gauge of the 
Snowdon pattern, which has a deep rim to enable it to catch snow as well 
as rain. It is provided w^ith a copper overflow bucket in case the glass 
