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Place of observation.

634

(Nos. 1 to 12.)

Antarctic Ocean.

Observed for an aggregate period of 505 days, as described in the following table and notes appended :

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RELATIVE PREVALENCE OF WINDS FROM THE

DIFFERENT POINTS OF THE COMPASS.

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Ratio of resultant

to sum of winds.

Monsoon influences.

Direction.

Force.

Number of days.*

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1. Lat. 60 to 65° S., long. 150° to 175° W. 2. Lat. 62 to 65° S., long. 133° to 135 W.

3. Lat. 60° to 64° S., long. 84° to 117° W.

4. Lat. 60° to 62° S., long. 63° to 83° W.

5. Lat. 60 to 65° S.,

long. 5° to 50° W. 6. Lat. 60 to 65° S., long. 11° to 14° W. 7. Lat. 60° to 61° S., long. 12° to 14° E. 8. Lat. 60 to 65° S.,

loug. 28° to 47° E. 9. Lat. 60 to 61° S.,

long. 107° to 118° E. 10. Lat. 60° to 65° S., long. 95° to 115° E. 11. Lat. 60 to 65° S., long. 130° to 135° E. 12. Lat. 60 to 65° S.,

Winter!
Winter!

Winter1
[ Spring2

Summer2
Autumn2
Winter2
The year?
Winter3

Spring3
Winter4

3,0 1

10 412 417 212 8 15 10 17 0 4 6 6 1 6 S. 33

0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 S. 22 30 E. .92
0400 0 1 0 1 0 0 S. 17 13 W..30
1 0.0 0 1 0 0

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0 N. 31° 36' W..44
0 E. .71

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N. 38 24 W..59

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N. 38 47 E. .82

N. 80 E.

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N. 56 35 W..75
3 W.1.76
N. 48
N. 27 31 W..57

S. 75 W. .34

44

N. 89 W. .31

55

180

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1 Computed from observations made by Captain Cook, in the winter of 1773-4.

2 Computed from observations collected and classified at the United States Naval Observatory, under direction of Captain M. F. Maury.

3 Computed from observations made by Sir James Ross, in the winter and spring of 1842-3.

4 Computed from observations made by Captain Cook, in the year 1773.

5 Computed from observations made by Captain Cook, for 5 days, in 1773, together with those made hourly, under the direction of Commodore Wilkes, for 8 days, in February, 1840.

6 Computed from hourly observations made under the direction of Commodore Wilkes, for 5 days, in February, 1840.

7 Computed from observations made by Sir James Ross, for 12 days, in 1842 or 1843, combined with those made hourly by Commodore Wilkes, for 6 days, in 1839 or 1840.

ZONE No. 32.

LATITUDE 65° TO 70° SOUTH.

The material for this zone is derived from the observations of the Antarctic explorers, Cook, James Ross and Wilkes, for an aggregate period of 104 days.

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1 Computed from observations made by Captain Cook, in the year 1770.

2 Computed from observations made by Sir James Ross, in the year 1842.

3 Captain Cook was at this point January 17th, 1773, and found the wind E. S. E.

4 Computed from observations made under the direction of Commodore Wilkes, along the coast of the Antarctic Continent, in the

year 1840.

5 Computed from observations made by Sir James Ross, in the winter of 1842-3.

Ratio of resultant

to sum of winds.

Number of days.

ZONE No. 33.

LATITUDE 70° to 75° SOUTH.

The material for the study of the winds of this zone is derived from the observations of the Antarctic explorers, Captain Cook and Sir James Ross, for an aggregate period of 41 days.

(No. 1.)

Antarctic Ocean, longitude 106° to 108° west..

Computed from observations made by Captain Cook, for two days, in the winter of 1773-4, as follows::

North 1, East 1.

Direction of resultant N. 45° E.???

Ratio of resultant to sum of winds .71.

(No. 2.)

Antarctic Ocean, longitude 15° to 18° west.

Computed from observations made by Sir James Ross, for four days, in the spring of 1841, as follows:

N. E. 3, East 1.

Direction of resultant N. 55° 48' E.???

Ratio of resultant to sum of winds .94.

(No. 3.)

Antarctic Ocean, longitude 166° to 176° east.

Computed from observations made by Sir James Ross, for 35 days, in the winter of 1840-41, as follows:-

North 3, N. E. 4, E. N. E. 2, East 9, E. S. E. 4, S. E. 14, S. S. E. 4, South 4, S. S. W. 1, S. W. 4, W. S. W. 6, West 4, W. N. W. 2, N. W. 2, N. N. W. 1; calm 4

Direction of resultant S. 38° 42' E.?

Ratio of resultant to sum of winds .29.

ZONE No. 34.

LATITUDE 75° To 80° SOUTH.

Sir James Ross appears to be the only explorer who ever penetrated this zone, and the material for the study of its winds is therefore confined to his observations, which were made for a period of 34 days, in the winter of 1840-1, between the meridians of longitude 166° and 168° east from Greenwich, as follows:

North 2, N. N. E. 6, N. E. 9, E. N. E. 2, East 13, E. S. E. 4, S. E. 6, S. S. E. 4, South 3, S. S. W. 2, S. W. 6, W. S. W. 2, West 1, N. W. 6; calm 2.

Direction of resultant N. 88° 41' E.

Ratio of resultant to sum of winds .31.

ZONES Nos. 35 and 36.

LATITUDE 80° TO 90° SOUTH,

These zones have never been visited by man, and the character of the winds that blow over them is very much a matter of conjecture. From the analogy of the northern hemisphere, as well as from theory, we may suppose that they blow from some southerly point, and become more easterly as they advance. And this view is confirmed by the fact shown above that every computed resultant south of latitude 65° is easterly.

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Island of Saint Paul, Aleutian Islands, lat. 57° 2′ N. and long. 170° W. Observed by C. P. Fish, six times a day, from August 18, 1872, to May 31, 1873, and contained in the Annual Report of the Chief Signal Officer, U. S. A., for 1873

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N. 48 22 E. 1.23
N. 19 37 W..20

S. 81 E. .24

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3 N. 4° 35' E. .42
1 N. 78 46 W..34
10 N. 0 W..074
21 N. 65 1 E. .35
N. 1 28 E. .17
N. 17 30 W..47
4 N. 73 5 W..28
27 N. 53 26 W..28
45 N. 12 52 W..16

N. 38 16 W..27}|
76 N. 5 16 W..43
5 N. 77 18 W..32

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1 Computed from the resultants for the seasons.

This addendum to page 111 was obtained too late for insertion in its proper place.

WINDS OF THE GLOBE.

SERIES C. VELOCITY TABLES AND DEFLECTING FORCES.

VELOCITY TABLES.

THESE tables, and the accompanying Plates 13 and 25, are designed to elucidate the last of the series of questions proposed at the outset of this discussion, and to show the effect of combining the element of force or velocity, with that of time, in computing the mean direction of the wind. The question itself is a highly important one, for since the real point that we wish to arrive at is the mean direction and amount of the actual motion, or transfer, of the air that passes over any given place, it is obvious that if there is a difference in the velocity of winds from the different points of the compass, or over different sections of country, such as to materially affect the results that would be obtained if it were always and everywhere the same, all the computations in the foregoing pages must require correction, if they be not rendered in great measure worthless; for (where not expressly stated to the contrary) they were all made on the assumption that the velocity was uniform; or, which is the same thing, without any reference to the velocity. And, not. only so, but nearly all the observations that have ever been. taken, both by land and sea, must be thrown aside (for in very few of them has the velocity of the wind been attempted to be recorded), and the whole work of observation must be commenced anew.

This question can be determined only by observation and experiment. We can know nothing about it à priori. Difference of velocity may produce a very great effect upon the mean direction, or very little, or none all. The solution of this question must therefore be viewed as vital to the search for the laws of atmospheric circulation.

The accompanying tables, collected from Series B of this work, are designed to give a synoptical view of the elements on which a determination may be based, as derived from observations taken mainly in the United States by the observers that reported to the Smithsonian Institution, in the years 1854, 1855, 1856 and 1857. The laborious work required to obtain the results here presented, was performed, under the direction of the author, by his brother, Robert A. Coffin, A.M., of Conway, Massachusetts, and other assistants, the cost being defrayed by the

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Smithsonian Institution.'

Few of the observers possessing anemometers, the velocities were usually estimated in force numbers, which were reduced to miles per hour on the following scale:

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1

[From a monograph found among my father's unpublished writings, I extract the following statement in reference to these Velocity Tables, which were then incomplete, being in course of computation.-SELDEN J. COFFIN.]

"In the Winds of the Northern Hemisphere, 1853, this question was discussed, so far as the comparatively meagre data then at my command allowed, and the conclusion arrived at was, that, as a general thing, this difference of velocity, while it increases the magnitude of the resultant, does not appreciably affect its direction. The data on this continent from which I reached the above conclusion, consisted of observations taken at 103 different places, for an aggregate period of 397 months, or about 33 years, more than half of them being from Eastern and Middle States, and only an aggregate of about two years from States and Territories west of Ohio.

"In 1857, the Secretary of the Smithsonian Institution ordered a thorough and exhaustive discussion of the subject, based on the observations reported to the Institution for the years 1854-7, from 418 different places on this continent, for an aggregate period of 8589 months, or over 700 years, in which each observer noted the direction of the wind, usually three times a day, and affixed to each record a number from 0 to 10 to represent the velocity, according to the scale given above, based on the experiments of Rouse and Smeaton.

"The method of discussion was, first to group the places of observation into districts of moderate geographical extent, then to compute, for each district, the mean velocity of the winds, as estimated by the observers, both the lower current and that indicated by the motion of the clouds, for each of the eight principal points of the compass, for each season of the year, and for the whole year, counting all winds between the N. and E. points as northeast, those between S. and E. as southeast, etc., and finally to compute the resultant motion of each of the two currents, over each district, for each season of the year and the whole year, first from the actual motion estimated as above, and then, for the purpose of comparison, on the supposition that the winds from all directions moved with the same mean velocity. To carry out this plan required great labor, inasmuch as beside classifying the winds according to the points of the compass from which they came, the record of the estimated velocity at each separate observation, amounting in the aggregate to over three-fourths of a million, had to be translated into linear distance, or miles per hour. An aggregate of over 5 years of working time has been spent upon it. The work of classification was performed chiefly by ladies; that of translating into miles, which required only care and accuracy in applying the scale and summing up the results, by men competent for such work; while the trigonometrical resultants were mostly computed by Robert A. Coffin.

"The results corroborate the views advanced in The Winds of the Northern Hemisphere in regard to the magnitude of the resultants, but not in regard to their direction, both of which facts will appear from the following general statements, in which it will be seen that the effect of difference in velocity is to throw the resultant northerly far more frequently than southerly, and at a much greater angle; that it increases its magnitude far more frequently than it diminishes it, and by a greater amount.

"In 10 districts north of the 45th parallel of latitude it is thrown northerly; in 9 at an average

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