122 
DETERMINATION OF ALTITUDES BY BAROMETER, 
which Avere referred to the level of the camp itself. The following tables exhibit the original 
data and the results deduced by each of the three different methods of computation. It will 
he seen that the altitudes of forty-eight stations were determined, the highest of which was 
2,809.5 feet above, and the most distant 36.4 miles from, the depot camp. Assuming the altitudes 
found by the level to be correct, a little calculation will show that the old method, the new 
method with observed air temperature, and the new method with mean daily air temperature, 
give mean errors of 29.3, 28.9, and 9.2 feet; maximum errors of 142, 119.1, and 31.9 feet; 
and minimum errors of 1.8, 1.5, and 0.8 feet, respectively; and also, that about two-thirds of the 
altitudes determined by the last named method differ from the true heights less than nine feet. 
COMPARISON OF THE DIFFERENT METHODS OF COMPUTING ALTITUDES FROM BAROMETRIC OBSERVATIONS, 
BASED UPON DATA OBTAINED IN THE SURVEY OF CANADA DE LAS UVAS, BY LIEUTENANT R. S. WIL¬ 
LIAMSON, UNITED STATES TOPOGRAPHICAL ENGINEERS, IN 1853. 
Data.—Observations in Depot camp during survey of Canada de las Uvas. 
Date. 
Hour. 
Reading of 
barometer. 
Att. 
therm. 
Det. 
therm. 
Date. 
Hour. 
Reading of 
barometer. 
Att. 
therm. 
Det. 
therm. 
1853. 
h. m. 
Inches. 
o 
o 
1853. 
h. m. 
Inches. 
o 
o 
Sept. 28 _ 
6. 00 a. m. 
28. 060 
58. 5 
59. 0 
Oct. 2. 
5. 30 p. m. 
28.730 
76. 0 
76. 5 
9. 00 a. m. 
28. 090 
71.5 
71. 0 
8. 40 p. m. 
28.752 
77. 0 
77.0 
12.00 m. 
28. 666 
79. 0 
79.5 
Oct. 3. 
6. 00 a. m. 
28.755 
62.5 
63.0 
3. 00 p. m. 
28. 623 
84. 0 
83. 0 
9. 00 a. m. 
28. 813 
85. 0 
84. 0 
5. 35 p. in. 
28. 595 
72. 0 
72. 0 
12. 00 m. 
28.782 
95. 0 
95.5 
8. 05 p. m. 
28. 610 
66. 0 
68.0 
3. 30 p. m. 
28.732 
96. 0 
95. 5 
Sept. 30_ 
6. 00 a. m. 
28. 609 
59. 5 
60.0 
5. 30 p. m. 
28. 710 
86.0 
85.0 
9. 00 a. m. 
28. 680 
80.5 
80. 0 
7. 30 p. m. 
28. 720 
75. 0 
74.5 
12.00 m 
28. 674 
95. 0 
94. 0 
Sept. 29_ 
5. 30 p. m. 
28. 560 
77.5 
77. 0 
3. 00 p. m. 
28. 650 
94. 0 
94. 0 
Sept. 30... 
6. 00 a. m. 
28. 609 
59. 5 
60. 0 
5. 30 p. m. 
28. 615 
83.0 
82. 5 
I 
l 
1 
1 
I 
O 
o 
6. 00 a. in. 
28. 688 
65.0 
66. 0 
8. 10 p. m. 
28. 656 
80. 0 
80. 0 
Oct. 4. 
5. 30 p. m. 
28. 680 
80.0 
80. 5 
Oct. 1. 
6. 00 a. m. 
28. 688 
65. 0 
66. 0 
Oct. 5. 
6. 00 a. m. 
28.724 
73.0 
72.5 
9. 00 a. m. 
28.759 
85. 0 
84.0 
Oct. 2. 
6. 00 a. m. 
28. 728 
63. 0 
65. 0 
12. 00 in. 
28. 758 
94. 5 
93. 5 
5. 30 p. m. 
28.730 
74. 0 
76. 5 
3. 00 p. m. 
28.715 
96. 0 
95. 0 
Oct. 3._ 
6. 00 a. m. 
28.755 
62.5 
63. 0 
5, 30 p. in. 
28. 690 
83.0 
83. 0 
9. 00 a. m. 
28. 813 
85. 0 
84. 5 
8. 00 p. m. 
28. 710 
80. 0 
80. 0 
12. 00 m. 
28. 782 
95. 5 
95. 0 
Oct. 3_ 
6. 00 a. m. 
28. 728 
65. 0 
63. 0 
3. 30 p. m. 
28.732 
96. 0 
95.5 
9. 00 a. m. 
28. 792 
81.5 
81.0 
5. 30 p. m. 
28. 710 
86. 0 
85. 0 
12. 00 m. 
28. 758 
93. 0 
92.0 
Oct. 4. 
6. 00 a. m. 
28. 751 
73. 0 
73. 0 
3. 00 p. m. 
28. 750 
94. 0 
93. 5 
K 
