If the measure of a height rather greater than the aneroid will commonly show, be required, it may be re-set thus—When at the upper station (within its range), and having noted the reading carefully, touch the screw behind so as to bring back the hand a few inches (if the instrument will admit), then read off and start again. Reverse the operation when descending. This may add some inches of measure approximately.
In the following Table, the difference between the number of feet opposite the height of a barometer, at one station, and that at another station, is their approximate difference of height.
TABLE.
| Barometer Inches. | Height in feet. | Barometer Inches. | Height in feet. | Barometer Inches. | Height in feet. |
| 31·0 | 0 | 26·8 | 3829 | 22·7 | 8201 |
| 30·9 | 85 | 26·7 | 3927 | 22·6 | 8317 |
| 30·8 | 170 | 26·6 | 4025 | 22·5 | 8434 |
| 30·7 | 255 | 26·5 | 4124 | 22·4 | 8551 |
| 30·6 | 341 | 26·4 | 4223 | 22·3 | 8669 |
| 30·5 | 427 | 26·3 | 4323 | 22·2 | 8787 |
| 30·4 | 513 | 26·2 | 4423 | 22·1 | 8906 |
| 30·3 | 600 | 26·1 | 4524 | 22·0 | 9025 |
| 30·2 | 687 | 26·0 | 4625 | 21·9 | 9145 |
| 30·1 | 774 | 25·9 | 4726 | 21·8 | 9266 |
| 30·0 | 862 | 25·8 | 4828 | 21·7 | 9388 |
| 29·9 | 950 | 25·7 | 4930 | 21·6 | 9510 |
| 29·8 | 1038 | 25·6 | 5033 | 21·5 | 9632 |
| 29·7 | 1126 | 25·5 | 5136 | 21·4 | 9755 |
| 29·6 | 1215 | 25·4 | 5240 | 21·3 | 9878 |
| 29·5 | 1304 | 25·3 | 5344 | 21·2 | 10002 |
| 29·4 | 1393 | 25·2 | 5448 | 21·1 | 10127 |
| 29·3 | 1482 | 25·1 | 5553 | 21·0 | 10253 |
| 29·2 | 1572 | 25·0 | 5658 | 20·9 | 10379 |
| 29·1 | 1662 | 24·9 | 5763 | 20·8 | 10506 |
| 29·0 | 1753 | 24·8 | 5869 | 20·7 | 10633 |
| 28·9 | 1844 | 24·7 | 5976 | 20·6 | 10760 |
| 28·8 | 1935 | 24·6 | 6083 | 20·5 | 10889 |
| 28·7 | 2027 | 24·5 | 6190 | 20·4 | 11018 |
| 28·6 | 2119 | 24·4 | 6297 | 20·3 | 11148 |
| 28·5 | 2211 | 24·3 | 6405 | 20·2 | 11278 |
| 28·4 | 2303 | 24·2 | 6514 | 20·1 | 11409 |
| 28·3 | 2396 | 24·1 | 6623 | 20·0 | 11541 |
| 28·2 | 2489 | 24·0 | 6733 | 19·9 | 11673 |
| 28·1 | 2582 | 23·9 | 6843 | 19·8 | 11805 |
| 28·0 | 2675 | 23·8 | 6953 | 19·7 | 11939 |
| 27·9 | 2769 | 23·7 | 7064 | 19·6 | 12074 |
| 27·8 | 2864 | 23·6 | 7175 | 19·5 | 12210 |
| 27·7 | 2959 | 23·5 | 7287 | 19·4 | 12346 |
| 27·6 | 3054 | 23·4 | 7399 | 19·3 | 12483 |
| 27·5 | 3149 | 23·3 | 7512 | 19·2 | 12620 |
| 27·4 | 3245 | 23·2 | 7625 | 19·1 | 12757 |
| 27·3 | 3341 | 23·1 | 7729 | 19·0 | 12894 |
| 27·2 | 3438 | 23·0 | 7854 | 18·9 | 12942 |
| 27·1 | 3535 | 22·9 | 7969 | 18·8 | 13080 |
| 27·0 | 3633 | 22·8 | 8085 | 18·7 | 13219 |
| 26·9 | 3731 | ||||
MARINE BAROMETER,
ADOPTED BY
HER MAJESTY'S GOVERNMENT,
On the recommendation of the Kew Observatory Committee of the
British Association for the Advancement of Science.
This instrument should be suspended in a good light for reading, but out of the reach of sunshine or the heat of a fire or lamp. It should be as nearly amidships, and exposed as little to sudden changes of temperature, gusts of wind, or injuries, as possible. In a ship of war it should be below the lowest battery or gun-deck. Light should have access to the back of the tube, to admit of setting the index so as to have its lower edge a tangent to the surface of the mercury—the eye being on the same level, which is known by the back and front edges of the index being in one line with the mercury surface. White paper or card will reflect light for setting the vernier correctly. The height of the cistern above or below the ship's water-line should be ascertained, and entered on the register.