ME, W. CEO ORES OR THE ATOMIC WEIGHT OF THALLIUM. 
319 
These logarithms, when increased by 0-000030, agree with those employed by Professor 
Miller in his determination of the value of the new standard pound (see Phil. Trans, 
for 1856) when working in the cellar under the Mineralogical Museum at Cambridge, 
in lat. 52° 12' IS", about 8 metres above the mean level of the sea ; increased by 0-000002 
they can be used in reducing weighings in Somerset House, lat. 51° 30' 40", 29-56 metres 
above sea-level ; or diminished by 0-000102 for weighings made in Paris. 
We have next to consider the influence exerted by the hygrometric state of the atmo- 
sphere, or, in other words, the influence of the vapour of water suspended in the atmo- 
sphere. It is clear that the moist air is nothing more than a mixture of v cubic inches 
of dry air at t° under a pressure minus that of the vapour, and of v cubic inches of 
vapour at t° and the pressure resulting from the hygrometric condition. Biot, 
Kegxault, and Biaxchi have ascertained that the pressure of vapour in an ordinary dry 
room is two thirds of the maximum pressure due to the temperature. 
Table B. — Values of 0-378 xf'G, where v t is the maximum pressure of vapour at the 
temperature t, in millims. of mercury at 0°, according to Eegxault’s observations*. 
i. 
0. 
1 . 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 
0 
1-16 
1-17 
1-18 
1-18 
1-19 
1-20 
1-21 
1*22 
1-23 
1-24 
1 
1-25 
1-25 
1-26 
1-27 
1-28 
1-29 
1-30 
1-31 
032 
1-33 
2 
1-34 
1-35 
1-36 
1-37 
1-37 
1-38 
1-39 
1-40 
1-41 
1-42 
3 
1-43 
1-44 
1-45 
1-46 
1-47 
1-48 
1-49 
1-50 
1-51 
1-53 
4 
1-54 
1-55 
1-56 
1-57 
1-58 
1-59 
1-60 
1-61 
1-63 
1-64 
5 
1-65 
06 6 
1-67 
1*68 
1-69 
1-70 
1-72 
1-73 
1-74 
1-75 
6 
1-76 
1-78 
1-79 
1-80 
1-81 
1-S2 
1-84 
1-85 
1-86 
1-87 
7 
1-89 
1-90 
1-91 
1-93 
1-94 
1-95 
1-96 
1-98 
1-99 
2-01 
8 
2*02 
2-03 
2-05 
2-06 
2-08 
2-09 
2-10 
2*] 2 
2-13 
2-15 
9 
2-16 
2-17 
2-19 
2 % 2\ 
G)%cycy 
2*24 
2-25 
2*27 
2-28 
2-29 
10 
2-31 
2-32 
2-34 
2-35 
2-37 
2-39 
2-40 
2 # 42 
2-44 
2-45 
11 
2-47 
2-48 
2-50 
2* 2 
2-53 
2.-55 
2-57 
2-58 
2-60 
2-62 
12 
2-64 
2-65 
2-67 
2-69 
2-71 
2-72 
2-74 
2-76 
2-78 
2-80 
13 
2-81 
2-83 
2-85 
2-87 
2-89 
2-91 
2-93 
2-94 
2-96 
2-98 
14 
3-00 
3-02 
3-04 
3-06 
3-08 
3-10 
3-12 
3-14 
3-16 
3-18 
15 
3-20 
3-22 
3-24 
3-26 
3-28 
3-31 
3-33 
3-35 
3-37 
3-39 
l6 
3-41 
3*43 
3-46 
3-48 
3-50 
3-52 
3-54 
3-57 
3-59 
3-61 
17 
3-63 
3-66 
3-68 
3-71 
3-73 
3 - 75 
3-78 
3-80 
3-82 
3-85 
18 
3-87 
3-90 
3-92 
3-95 
3-97 
4-00 
4-02 
4-04 
4-07 
4-09 
19 
4-12 
4-15 
4-17 
4-20 
4-22 
4-25 
4-28 
4-30 
4-33 
4-36 
20 
4-38 
4-41 
4-44 
4-47 
4-49 
4-52 
4-55 
4-58 
4-61 
4-63 
21 
4-66 
4-69 
4-72 
4*75 
4-78 
4-81 
4-84 
4*87 
4-90 
4.90 
22 
4-95 
4-99 
5-02 
. 5-05 
5-08 
5-11 
5*14 
5-17 
5-20 
5-23 
23 
5-26 
5-30 
5' 33 
5*36 
5-39 
5-43 
5-46 
5*49 
5-52 
5-56 
24 
5-59 
5-62 
5-66 
5-69 
5-73 
5-76 
5-80 
5-83 
5-87 
5-90 
25 
5-93 
5-97 
6-01 
6-04 
6-08 
6-12 
6-15 
6-19 
6”22 
6-26 
26 
6-30 
6-34 
6-37 
6-41 
6-45 
6-49 
6-53 
6*56 
6-60 
6-64 
27 
6-68 
6*72 
6-75 
6-79 
6-83 
6*87 
6-91 
6-95 
6-99 
7-03 
28 
7-08 
7-12 
9-17 
7-21 
7-25 
7-29 
7-34 
7-38 
7-42 
7-46 
29 
7-51 
7"55 
7-59 
7-64 
7-68 
7-73 
7-77 
7-82 
7-86 
7-91 
30 
7-95 
8-00 
8-04 
8-09 
8-14 
8-18 
8-23 
8 28 
8-23 
8-37 
The formula employed for the calculation of the true weight of a substance in vacuo, 
* Annales de Chimie, 1845, 3 me serie, tome xv. p. 138. 
2 U 2 
