ON ATMOSPHERIC WAVES. 115 
The passages of maxima about or not far removed from the 3rd of each 
monta, appears to have failed at Greenwich for April and May. On turning, 
however, to the Greenwich records we find maxima within 12 hours of the 
epochs at Toronto of the following values, when corrected for sea level. April 
2, 14 hours, 29:815 ; May 3, 4 hours, 29°851. It consequently appears that the 
two series so far agree in the general fact, that about the 3rd of each month 
for the period included in the tables, the barometer passed maxima on both 
sides of the Atlantic, the excursions above or below the gauge-point at Green- 
wich being much greater than those at Toronto. 
Upon a still closer comparison of the maxima at both stations, it appears 
highly probable that, with few exceptions, they are nearly contemporaneous, 
the excursions at Greenwich being, as just noticed, by far the greatest. It 
is a matter of regret that at present this most interesting subject cannot be 
followed out in all its details, and that the announcement cannot extend much 
beyond the high probability that during nearly eight months of the year 1841 
the barometric movements on both sides of the Atlantic (Toronto and Green- 
wich being at present the extreme stations) were connected, in so far as the 
observations indicate a tendency to increased pressure at both stations at 
nearly the same epochs, and that these epochs appear to observe some regu- 
larity, exhibiting a periodicity of about 30 days’ interval, especially that of 
maximum pressure, about the 3rd of each month, which is clearly traced at 
both stations. The greater excursions at Greenwich, the insular station, are 
perfectly in accordance with facts of a similar character developed in the 
course of the reduction of meteorological observations (see Sir John Her- 
schel’s Report in the volume for 1843). 
A comparison of the Table of Barometric Maxima in the Greenwich Abs- 
tracts, with a similar table in the 15th volume of the Memoirs of the Royal 
Academy of Brussels, p. 17, leads to the same result as that obtained from 
a comparison of the Greenwich and Toronto observations, in so far as the 
absolute maxima at both stations, Greenwich and Brussels, are not in all 
cases contemporaneous, or separated only by a short interval. The table 
alluded to gives only one maximum in the month, the highest reading. In 
the Greenwich records we find corresponding maxima to these, with short 
intervals between the transits at each station. From a consideration of the 
two series of maxima the following Table has been formed. 
Tas_e_e IIL. 
Exhibiting the symmictrical disposition of Barometric Waves on each side 
a central Axis, June 3: 22, 1841. ; 
Month. Epoch. Altitude. | Interval. | Wave. 
a in. dh 
March...... 10 22 30°572 138 2 6 
es 24 0 329 20 10 5 
April .......) 13 10 +202 13 0 4 
Ht 26 10 180 17 10 3 
May.........| 13 20 441 10 0 2, 
Es 23 20 260 ll 2 1 
JUNE seceeee 3 22 426 Axis. 
B 15 22 289 12 0 1 
a8 27 14 ‘179 11 16 2 
July ........ 912 | ‘019 11 22 3 
s 24 10 +232 14 22 4 
August ..... 12 10 010 19 0 5 
£ 26 10 30°353 14 0 6 
12 
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