Scotia? We require results on the south shores of Newfoundland, and on the Great Bank, to give us clear ideas on these points, and I hesitate to extend the generalization to this tempting field.

The Shoals from Nantucket and broken ground near George's Bank, and the comparatively shoal water in their vicinity on the one side, and the Great Bank of Newfoundland on the other, look as if full of meaning of this sort. Further results may, however, show that this is not the interpretation of the phenomena. The tides of Labrador are but 2.3 feet, bringing us back to the standard of Hatteras, and of Montauk Point, and what probably would be that of Nantucket, but for interferences.

The complicated character of the cotidal lines in this immediate vicinity is indicated by the chart, the lines from XII. to XV. hours being crowded into the very small space of a few miles on the south side of Nantucket.

To return to the more limited scale, within which our inductions are safe, Delaware Bay, New York Bay, Long Island Sound, Narragansett and Buzzard's Bays, Nantucket and the Vineyard Sounds, present, on a smaller scale, the same phenomena of increase in the height of the tide in ascending. On the contrary, in Chesapeake Bay, which widens and changes direction at a right angle immediately from the entrance, the tides diminish in height, as a general rule, in going up the bay.

The results of the heights of tides along the coast are very satisfactorily shown, upon a model which is now before the Association, for superintending the execution of which I am indebted to Mr. Pourtales. The basis is a map of the Atlantic coast from Cape Florida to Cape Race, upon which the cotidal lines of the United States are traced. The tidal stations are marked upon this, and rods cut to length, and proportionate to the rise and fall of the tides at the several stations, are inserted in holes drilled at the station points. The steel rods refer to the heights at exterior stations, and the brass rods to interior ones. Paper cut to the form of the general curve of heights, which has already been explained, and placed behind these rods, serves to show the generalizations with great distinctness.

I propose to call the bay between Cape Florida and Cape Hatteras, the Southern Bay; that between Cape Hatteras and Nantucket, the

Middle Bay; and that between Nantucket and Cape Sable, the Eastern Bay, of the coast of the United States.

The general figure of the coast line has of course heretofore attracted the attention of geographers. The connection with the heights of the tides could only satisfactorily be made out by such a series of tidal observations as those embraced in the Coast Survey.

V. METEOROLOGY.

1. ON THE WINDS OF THE WESTERN COAST OF THE UNITED STATES, FROM OBSERVATIONS IN CONNECTION WITH THE U. S. COAST SURVEY. By. A. D. BACHE, Superintendent.

[Communicated by authority of the Treasury Department to the American Association for the Advancement of Science.]

THE observations, of which I propose at present to communicate the results, were made in the year 1855, in connection with the tidal observations on the Pacific coast, at three permanent stations San Francisco, and San Diego.

Astoria,

The approximate latitude and longitude of each of the stations are as follows: Astoria, Oregon, lat. 46° 11′ N., long. 123° 49′ W.; San Francisco, California, lat. 37° 48′ N., long. 122° 28′ W.; San Diego, California, lat. 32° 40′ N., long. 117° 12′ W.

The mode of observing was that described in my paper on the winds at Cat Island, read before the Association in 1850. The observers were posted and practised together by Lieutenant W. P. Trowbridge, of the U. S. Corps of Engineers, under whose supervision the observations were made.

The directions of the winds were noted in points, and the force in .he conventional scale before referred to. These numbers were reduced to velocity in miles per hour, by the tables given in my former paper, and the quantity of wind blowing from any quarter during a given period was thence readily found.

The tables and diagrams are thus of the same kind as those which I have before presented to the Association. They were made under the direction of Assistant L. F. Pourtales, of the U. S. Coast Survey, to whose care, assiduity, and knowledge I am indebted for the opportunity of presenting them. The computations and diagrams were

made by Miss Mary Thomas.

The observations were taken three times each day, at 6 A. M. and P. M., and at noon, except on Monday of each week, when hourly observations took the place of the regular daily ones. From these latter results the reference of the three daily observations to the mean of the day has been made.

The quantities of wind for each hour and for each direction were computed and grouped by months, and then plotted. The eye readily takes in the characteristics of the winds at different periods of the day and year, and for the various directions. To apply these to the reduction of the daily observations, tables were formed of the average time during which each wind blowing would give from observations at the three hours already named the result for the day. For example, the west wind at San Francisco gave for the quantity in twenty-four hours by the daily observations, 505. The mean hourly quantity at 6 A. M. being six, at 12 M., twenty-seven, and at 6 P. M., thirty-one. These quantities respectively, being supposed continued for nine hours, five hours, and ten hours, which agrees with the diagram, would give 499, a number differing but little from the total found for the day. In this way the following table was formed, which was applied to the reductions of the daily observations.

Wind.

TABLE FOR DEDUCING FROM THE THREE DAILY OBSERVATIONS THE MEAN

ASTORIA.

OF THE DAY.

SAN FRANCISCO.

SAN DIEGO.

From the tables of velocities in miles per hour, deduced from the observations by the method just explained, the following table of quantities of wind from different directions for each month is found. The rhumbs are written at the top of the table, the months at the side, and at the meeting point of a vertical and horizontal line from the head and side titles are found the quantities. The last column at the side of the table gives the total quantities for the several months, and below is found the total for each direction for the year.

16*