146 
POPULAR SCIENCE REVIEW. 
G-laisher’s Multipliers. 
Readings of the Dry Bulb 
Thermometer. 
Multiplier. 
Readings of the Dry Bulb 
Thermometer. 
Multiplier. 
o 
20 
8*1 
33 
30 
21 
7-9 
34 
2-8 
22 
7-6 
35 
2-6 
23 
7-3 
36 
2-5 
24 
6-9 
37-8 
2-4 
25 
6-5 
39-41 
2-3 
26 
61 
42-45 
2-2 
27 
5-6 
46-50 
21 
28 
5-1 
51-56 
20 
29 
4-6 
57-64 
1*9 
30 
42 
65-73 
1-8 
31 
3-7 
74-86 
17 
32 
3-3 
1 
87-90 
1-6 
Rule. — Multiply the difference between the two thermome- 
ters by the multiplier corresponding to the temperature of the 
dry bulb one, and subtract the product from this temperature ; 
then the remainder will be the temperature of the dew point. 
O 
Example : — Let dry hulb tliermometer=58 
Let wet bulb thermometer=51 
Difference = 7 
Then 7xl’8=13‘3. 
Then, dew point equals 58° — 13‘3=427° 
Lieut. Noble has drawn up a table of factors considered to 
be more accurate than these. 
It may be observed, that there are many substances to be met 
with in nature which are extremely sensitive to variations in 
the humidity of the atmosphere, and which may be used as 
hygroscojpes , such as wood, ivory, quills, hair, whalebone, animal 
membranes, catgut, &c. 
A knowledge of the dew point puts us in the track of much 
other information connected with atmospheric aqueous vapour, as 
will be seen from an examination of Grlaisher’s Tables ; but the 
amateur had better disregard such minutise, or he will get 
bewildered. 
Barometrical Observations. — The barometer measures the 
pressure or density of the atmosphere. The meteorologist will 
disregard the common notation, 4 Fair ,’ 4 Set Fair ,’ 4 Change,’ &c. 
These terms are not only antiquated and nearly obsolete, but are 
often misleading. In real truth, barometers are best without any 
remarks of this kind at all ; but inasmuch as the public does not 
