W. Ferrel—Meteorological effects upon the Tides. 345 
law of friction between the wind and the water. Very strong 
winds, therefore, may change the sea-level in Boston harbor a 
foot or more, and this agrees well with individual observations. 
Of about 700 tidal residuals of high water throughout the year 
1859, obtained from a comparison of computation by the for- 
mul and tables, with observations, only 10 amount to as much 
as one foot. If therefore, we, suppose that these residuals are 
due to the effects of the winds only, and no part of them to 
other disturbing causes, and to errors of the tidal formule and 
tables, even upon this supposition we know by actual measure- 
ments with the tide-guage, that in the course of a whole year, 
the sea-level of Boston harbor is not often changed by the 
winds as much as one foot. The popular impression of large 
changes of sea-level, no doubt arises from making observations 
on sloping beaches where a small perpendicular change of leve 
produces a very great apparent change 
An important meteorological result is shown in the fourth 
column of the preceding table, which is that the barometer 
during calms stands very near the maximum of all the ave- 
rages of the winds from the different quarters. This indicates 
that the winds generally are of a cyclonic character, prevailing 
mostly in the interior of the cyclone where there is barometric 
Meni: | Bo. alob| Become: | Gee Se iechy. | barometer. 
in. in. 
January 324 29°995) —-004 29°934 + ost 
February 310 30-007 020 +°053) 
h 363 29°886 043 —091 
April 34 29°957 6 —-043 
May 354 30-013 090 —.011! 
une 361 29-961 110 083 
July 354 30-020 121 —"035 
August 377 30°0 119 — "030 
360 30°71 104 +°066 
October 358 30-058 076 0 
November 335 99°947 046 +067 
December 320 30°055' —-020 +001 
The mean barometer at the height of 71 feet, and reduced to 
the temperature of 32°, is 29°934 in. Adding 0-082 in. for the 
