368 ~ A. A. Hazen—Thermometer Exposure. | 
foot below the inner roof. On the east and west are louvres to 
shield it from the rising and setting sun. In calm weather it 
radiation, and at night the same number of degrees too low by 
radiation to the sky and from surrounding objects. The 
Stevenson shelter is also in great favor in England, and con- 
sists of a cubical screen, of double louvres, 18” long and high 
and 10” wide. This is placed at a height of 4’ above sod. 
Professor Mohn, of Christiania, has shown that in the sun this 
shelter gives too high values. It is undoubtedly too small an 
close to give good results. A shelter similar to the above has 
_ been devised by Rev. F. W. Stow, of England. (Quart. Jour. 
et. Soe., vol. viii, p. 234.) This is somewhat larger than Ste- 
venson’s and has metallic louvres instead of wooden. It has 
the advantage of great ease in construction and of good ven- 
tilation. 
In Spain a double metallic shelter has been used. This has 
an inside louvre box 14X14X17 inches, between the inside 
and outside louvres there is a free air space and connected with 
this there is acommon vane ventilator. In Russia, Professor 
shelter is open to the objection that it prevents a free access of 
air, the double boarded south side cutting off all south wind 18 
It is of the utmost importance that there should be a stand- 
ard of comparison in all experiments, and this we have 10 the 
swung thermometer, called by the French thermometer fronde, - 
which is a common thermometer attached to a string or wire, 
and rapidly swung through a circumferance whose radius 38 
the length of the string. After experimenting some ume a 
. 
