copyright reserved 
j£' 
[ 26 ] 
116 
THE METEOROLOGICAL TABLES 
Some| 
Are prepared from my meteorological journal, kept on the road, 
of the columns may require an explanation. 
The column “boiling 'point of water” refers to my observations with 
two thermometers, constructed by my order, by J. W. Edmonds, of Boston, 
4 eadh varying from 85 to 100° Celsius, and every degree divided in tenths. 
/ I made many experiments with them on the road, to find the relative dif¬ 
ference between the boiling point of water and the mercurial column of 
my barometer. From about 50 such observations, made within the range 
of from 23 to 29 inches of the barometer, I abstracted the general result, 
that 1 inch of my barometer at the temperature of 32 Q Fahr., was == 
1°.04138 boiling point Therm. Gels., and 1° Th. C. = 0".96026 of the 
barometer. But, at the same time, I have come to the conclusion, as 
others before me, that the determination by the boiling point of water 
can never in correctness equal- the barometrical measurement. A differ-, 
ence in fuel, in water, in the size of the vessel, in draught of air, &c., is 
apt to produce such a discrepancy in the relative boiling point, that 
this method will answer well enough as a correlative proof of the barome¬ 
ter, and for heights, where several hundred feet, more or less, is not a 
matter of consideration, but that it will never be capable of supplying the 
place of the barometer. 
The dewpoint , found by excess of temperature of the dry over the wet 
bulb, is calculated according to “tables for the determination of.the dew¬ 
point,” given in the Encyclopaedia Britanica, and republished in the 
“Report to the Navy Department of the United States on American coals, 
by,Professor Walter R. Johnson : Washington, 1844.” Observations be¬ 
yond the reach of these tables, I calculated according to the rule given 
by Professor Espy : “ The dew-point, when it is not very low, may be 
nearly obtained by multiplying the difference between dry and wet bulb 
temperature with 103, dividing the result by the wet-bulb temperature, 
and subtracting the quotient from the dry-bulb temperature; the remainder 
will be the dew-point.” 
In the column “ wind” the force of the wind is designated, as recom¬ 
mended by Professor Espy, by numbers from 0 to 6; 0 being a calm, 1 
a very gentle breeze, 2 a gentle breeze, 3 a fresh wind, 4 a strong wind, 
5 a storm, and 6 a hurricane. 
The clearness of the sky is also marked in numbers from 0 to 10; 0 
representing entire cloudiness, and 10 entire clearness. 
... _* . '.** ■ 
