In Table XVI. of Mr. Baily, the Equation of equal Altitudes is given for the entire

interval of 24 hours, but it is seldom required beyond the above limits.

TABLE XV.

LENGTH OF A SECOND OF LATITUDE AND LONGITUDE IN FEET ON THE SURFACE OF THE EARTH, THE COMPRESSION BEING TAKEN AS 300.

Puissant, calculating the compression from the measurement of the great arc in France, obtains different results on different sides of the Meridian of Paris, making it as low as

2 on the side of the Atlantic, and 30s to the Eastward; which latter quantity is generally assumed on the Continent.

Correction in Feet.

TABLE XVI.

CORRECTIONS FOR CURVATURE AND REFRACTION.

Showing the difference of the Apparent and True Level in Feet, and Decimal parts of Feet, for Distances in Feet, Chains, and Miles.

Correction in Feet.

Correction in Feet.

100 00024 0000400020

150 00054 0000800046 20000096 00013 00083 25000149 00021 00128 300 00215 00031 00184 35000293 00042 00251 40000383 0005500328 450 00484 00069 00415 50000598 00085 00513 55000724 0010300621

600008610012300738 6500101000144 00866 70001172 00167 01005 750 01345 00192 01153 800 0153100219 01312 8500172800247 01481 90001938 00277 01661 950 021590030801851

3

8-1708 1.1673

7.0035

10.6720 1.5246

9.1474

5000261 0003700224
5.5 00315 00045 00270
60 00375 0005400321 4 13.5468 1.9295 11.5773

8

48.1910

6.8844 41.3066

7.7181 46-3089 8.5996 51-5975 66.7000 9.5286 57-1714 80-7070 11.5296 69.1774 96.0480 13.7211 82-3269 112-7230 16-1033 96.6197 130-7320 18.6760 112-0560 150-0750 21-4393 128-6357 170-7520 24.3931 146-3589 192-7630 27.5376 165.2254 216-1086 30.8727 185.2359 240-7870 34-3981 206-3889 266-8000 38.1143 228.6857

100002392 00333 02059 10-0 01042 0014900893
1050 02638 00377 02261 10.50114900164 00985 9 54.0270
11000289500414 02481 11.00126100180 01081 960-1971
11500316400452 02712 11.5 01378 00197 01181 10
1200 03445 00492 02953 12.00150100214 01287 11
1250 03738 00534 03204 12.50162800233 01395 12
1300 04043-0057803465 13.00176100252 01509 13
135004361 0062303738 13.501899 00271 01628 14
140004689 00670 04019 14.002043 00292 01751 15
1450-0503000719 04311 14.5 0219100313 01878 16
1500-0538300769 04614 150 02345 00335 02010 17
1550 05748 0082104927 15.5 02504 00358 02146 18
1600 0612500875 05250 16-002668 00381 02287 19
1650-06514 0093105583 16.5 02837 00405 02432 20
1700-06914 0098805926 17.003012-00430 02582
1750 07327 01047 06280 17.503192-0045602736
1800 07752 0110706645 18-00337700482 02895
1850-0818801170 07018 18.5035670050903058
190008637 01234 07403 19-003762.0053703225
1950-09098 01300 107798 19.5039630056603397
2000 09570 01367 08203 20-0 04169 0059603573

TABLE XVII.

REDUCTION IN LINKS AND DECIMALS UPON EACH CHAIN'S LENGTH FOR THE FOLLOWING VERTICAL ANGLES.

The following formula will serve for the comparison of these Thermometers.

The Logarithms answering to every degree of the graduations of the above Thermometers will be found at page 296, vol. i., of Dr. Pearson's "Practical Astronomy."