Table of Altitudes.
| Aneroid or Corrected Barometer. | Height in Feet. | Aneroid or Corrected Barometer. | Height in Feet. | Aneroid or Corrected Barometer. | Height in Feet. |
|---|---|---|---|---|---|
| in. | ft. | in. | ft. | in. | ft. |
| 31·00 | 0 | 26·76 | 4000 | 23·11 | 8000 |
| 30·94 | 50 | 26·76 | 4050 | 23.07 | 8050 |
| 30·88 | 100 | 26·67 | 4100 | 23.03 | 8100 |
| 30·83 | 150 | 26·62 | 4150 | 22.98 | 8150 |
| 30·77 | 200 | 26·57 | 4200 | 22·94 | 8200 |
| 30·71 | 250 | 26·52 | 4250 | 22·90 | 8250 |
| 30·66 | 300 | 26·47 | 4300 | 22·86 | 8300 |
| 30·60 | 350 | 26·42 | 4350 | 22·82 | 8350 |
| 30·54 | 400 | 26·37 | 4400 | 22·77 | 8400 |
| 30·49 | 450 | 26·33 | 4450 | 22·73 | 8450 |
| 30·43 | 500 | 26·28 | 4500 | 22·69 | 8500 |
| 30·38 | 550 | 26·23 | 4550 | 22·65 | 8550 |
| 30·32 | 600 | 26·18 | 4600 | 22·61 | 8600 |
| 30·26 | 650 | 26·13 | 4650 | 22·57 | 8650 |
| 30·21 | 700 | 26·09 | 4700 | 22·52 | 8700 |
| 30·15 | 750 | 26·04 | 4750 | 22·48 | 8750 |
| 30·10 | 800 | 25·99 | 4800 | 22·44 | 8800 |
| 30·04 | 850 | 25·94 | 4850 | 22·40 | 8850 |
| 29·99 | 900 | 25·89 | 4900 | 22·36 | 8900 |
| 29·93 | 950 | 25·85 | 4950 | 22·32 | 8950 |
| 29·88 | 1000 | 25·80 | 5000 | 22·28 | 9000 |
| 29·82 | 1050 | 25·75 | 5050 | 22·24 | 9050 |
| 29·77 | 1100 | 25·71 | 5100 | 22·20 | 9100 |
| 29·71 | 1150 | 25·66 | 5150 | 22·16 | 9150 |
| 29·66 | 1200 | 25·61 | 5200 | 22·11 | 9200 |
| 29·61 | 1250 | 25·56 | 5250 | 22·07 | 9250 |
| 29·55 | 1300 | 25·52 | 5300 | 22·03 | 9300 |
| 29·50 | 1350 | 25·47 | 5350 | 21·99 | 9350 |
| 29·44 | 1400 | 25·42 | 5400 | 21·95 | 9400 |
| 29·39 | 1450 | 25·38 | 5450 | 21·91 | 9450 |
| 29·34 | 1500 | 25·33 | 5500 | 21·87 | 9500 |
| 29·28 | 1550 | 25·28 | 5550 | 21·83 | 9550 |
| 29·23 | 1600 | 25·24 | 5600 | 21·79 | 9600 |
| 29·17 | 1650 | 25·19 | 5650 | 21·75 | 9650 |
| 29·12 | 1700 | 25·15 | 5700 | 21·71 | 9700 |
| 29·07 | 1750 | 25·10 | 5750 | 21·67 | 9750 |
| 29·01 | 1800 | 25·05 | 5800 | 21·63 | 9800 |
| 28·96 | 1850 | 25·01 | 5850 | 21·59 | 9850 |
| 28·91 | 1900 | 24·96 | 5900 | 21·55 | 9900 |
| 28·86 | 1950 | 24·92 | 5950 | 21·51 | 9950 |
| 28·80 | 2000 | 24·87 | 6000 | 21·47 | 10000 |
| 28·75 | 2050 | 24·82 | 6050 | 21·44 | 10050 |
| 28·70 | 2100 | 24·78 | 6100 | 21·40 | 10100 |
| 28·64 | 2150 | 24·73 | 6150 | 21·36 | 10150 |
| 28·59 | 2200 | 24·69 | 6200 | 21·32 | 10200 |
| 28·54 | 2250 | 24·64 | 6250 | 21·28 | 10250 |
| 28·49 | 2300 | 24·60 | 6300 | 21·24 | 10300 |
| 28·43 | 2350 | 24·55 | 6350 | 21·20 | 10350 |
| 28·38 | 2400 | 24·51 | 6400 | 21·16 | 10400 |
| 28·33 | 2450 | 24·46 | 6450 | 21·12 | 10450 |
| 28·28 | 2500 | 24·42 | 6500 | 21·08 | 10500 |
| 28·23 | 2550 | 24·37 | 6550 | 21·05 | 10550 |
| 28·18 | 2600 | 24·33 | 6600 | 21·01 | 10600 |
| 28·12 | 2650 | 24·28 | 6650 | 20·97 | 10650 |
| 28·07 | 2700 | 24·24 | 6700 | 20·93 | 10700 |
| 28·02 | 2750 | 24·20 | 6750 | 20·89 | 10750 |
| 27·97 | 2800 | 24·15 | 6800 | 20·85 | 10800 |
| 27·92 | 2850 | 24·11 | 6850 | 20·82 | 10850 |
| 27·87 | 2900 | 24·06 | 6900 | 20·78 | 10900 |
| 27·82 | 2950 | 24·02 | 6950 | 20·74 | 10950 |
| 27·76 | 3000 | 23·97 | 7000 | 20·70 | 11000 |
| 27·71 | 3050 | 23·93 | 7050 | 20·66 | 11050 |
| 27·66 | 3100 | 23·89 | 7100 | 20·63 | 11100 |
| 27·61 | 3150 | 23·84 | 7150 | 20·59 | 11150 |
| 27·56 | 3200 | 23·80 | 7200 | 20·55 | 11200 |
| 27·51 | 3250 | 23·76 | 7250 | 20·51 | 11250 |
| 27·46 | 3300 | 23·71 | 7300 | 20·47 | 11300 |
| 27·41 | 3350 | 23·67 | 7350 | 20·44 | 11350 |
| 27·36 | 3400 | 23·62 | 7400 | 20·40 | 11400 |
| 27·31 | 3450 | 23·58 | 7450 | 20·36 | 11450 |
| 27·26 | 3500 | 23·54 | 7500 | 20·32 | 11500 |
| 27·21 | 3550 | 23·50 | 7550 | 20·29 | 11550 |
| 27·16 | 3600 | 23·45 | 7600 | 20·25 | 11600 |
| 27·11 | 3650 | 23·41 | 7650 | 20·21 | 11650 |
| 27·06 | 3700 | 23·37 | 7700 | 20·18 | 11700 |
| 27·01 | 3750 | 23·32 | 7750 | 20·14 | 11750 |
| 26·96 | 3800 | 23·28 | 7800 | 20·10 | 11800 |
| 26·91 | 3850 | 23·24 | 7850 | 20·07 | 11850 |
| 26·86 | 3900 | 23·20 | 7900 | 20·03 | 11900 |
| 26·81 | 3950 | 23·15 | 7950 | 19·99 | 11950 |
| 26·76 | 4000 | 23·11 | 8000 | 19·95 | 12000 |
This Table is intended more particularly for the graduation of aneroids with a circle of measures in feet concentric with the ordinary circle of barometric height measured in inches. The circle of feet is to be read off, at the upper and lower stations, by the index; and the rule for measuring the height will be: Subtract the reading at the lower station from the reading at the upper station; the difference is the height in feet.
Example.
| In. | Ft. | |
| Barometer at Upper Station, | 23·50 | 7550 |
| ” Lower ” | 24·20 | 6750 |
| Actual height | 800 | |
| There is no correction for temperature required with aneroids which are “compensated.” | ||
In using the instrument here described in the measurement of altitudes, the movable needle point which is turned by the mill-edged rim is set opposite the index hand. This is to be done at the foot of the mountain or hill. Then the difference between the index hand and the movable needle point will be the number of feet ascended (vide Table appended, and “Example”). Suppose the index hand stand when at the foot of the hill at 30in. 10⁄100, and when you again look at the instrument you find the index hand has gone back, or has fallen to 29in. 12⁄100, then you would have ascended 900ft.
At [page 26] of this work we referred to the hypsometrical or boiling-point apparatus used in taking altitudes. Since the remark there made was penned we have endeavoured, and we hope successfully, to so guard the improved form of aneroid barometer, referred to at p. 741, from the chance of accident, that it can be safely carried by the explorer of even the most rugged and inhospitable regions.
On the Use of the Sextant and Artificial Horizon.
We do not propose in this work to trespass on the province of books on nautical astronomy. We take it for granted that every traveller using a sextant will also provide himself with an Epitome—Norie’s, Rapers, or Kerigan’s (of course the latest possible edition of either), and with the “Nautical Almanac,” which may be had for three years in advance, by persons contemplating a long journey.