



New York AgricutTuRAL Experiment STATION. OT1 
- There are hygrometers so made that one can read directly from 
- the instrument the per cent of moisture and need not, therefore, 
use any tables.or make any calculations. Hygrometers of any 
desired form can be furnished by any house dealing in physical 
apparatus, such as that of James W. Queen & Co., Philadelphia, 
or Eimer & Amend, New York City. 
Suppose one desires to hold the temperature of a room between 
50° F. and 65° and have the air contain from eighty to ninety-five 
per cent as much moisture as it can hold. How can one find 
how much apart the dry-bulb and wet-bulb thermometers should 
be? We turn to the left hand column in the table and find 
50° F.; we then follow the column horizontally to the right until 
we come to the figure ninety-five. We then follow this column 
up vertically and find at the head the figure 0.7° F’. which: means 
that if the dry-bulb thermometer is 0.7° F. higher than the wet- 
bulb thermometer, the air contains ninety-five per cent as much 
moisture as it can hold, or the highest limit we want. We, then, 
in a similar manner, find that at 65° F. the two thermometers 
will be 3.6° F. apart when the air holds eighty per cent moisture, 
the lowest limit we want. Therefore, if we keep our two ther- 
mometers within 8° F. of each other and between the tempera- 
tures of 50° F. and 65° F., we shall have a degree of moisture 
varying from eighty to ninety-five per cent of saturation. 
One precaution should be emphasized in reference to reading 
the themometer. Before one takes a reading, a current of air 
should be passed over the hygrometer. This may be done by 
fanning the instrument with the hand gently just before reading 
-off the temperature. The object of this is to make sure that the 
air in contact with the wet-bulb thermometer is as dry as the rest 
-of the air in the room; owing to evaporation, the air around the 
wet-bulb thermometer may contain more moisture than the rest 
of the airin the room. By bringing into contact with the wet- 
bulb thermometer some less moist air, more water evaporates, and 
the greater will be the difference between the readings of the 
two thermometers. 
Fleischmann states that the air in a cheese-curing room or cel- 
lar (kasekeller) should never gu below 10° C. (50° F.), and never 
above 18° C. (64.4° F.). The moisture should not drop below 
sixty-five per cent of saturation. 
