il 
370 Proceedings of the British Association. 
The line of mean pressure occurred between the hours of 1 and 
2, and between 7 and 8, A. M.; and again between 12 and 1, and 
between 6 and 7, P. M. The hourly maximum pressure was at 
10 o’clock, morning and night; being, with only one exception, 
the uniform result for six years. The hourly minimum pressure 
occurred at 4, A. M. and P. M., being the uniform result for six 
years, without any exception. ‘The line of mean pressure was 
crossed four times in the 24 hours; and thus was realized, in the 
midst of atmospheric disturbances of very corisiderable amount, 
that effect, termed horary oscillation, which was first observed 
by Baron Humboldt, in tropical climates. Mr. Airy, to whom 
these observations were submitted, seemed to think, that but lit- 
tle now could be effected by continuing them after the close of 
this year. There had been 48,000 hourly observations on the 
atmospheric pressure, and 87,000 hourly observations on the tem- 
perature: and he trusted these would not be preserved merely in 
the perishable form of manuscript, but placed at the disposal of the 
scientific world. After explaining the construction of Whewell’s 
anemometer, he said, that when the pencil tracing the integral 
effect of the wind, moved at the rate of one tenth of an inch per 
hour, the current of air at the same time moved at a mean rate of 
eleven feet per second. He (Mr. H.) had, by means of this in- 
strument, endeavored to arrive at something like an approxima- 
tion to the velocity and direction of what he believed would 
amount to a ¢rade-wind. He had a table of results which gave 
the mean velocity of the wind, in feet per second, for each month 
of the year, viz. 
Feet per sec, Feet per sec. 
April, —- 13. October, = - 15.29 
May, a2 IR November, - 14.96 
Jone, 85g IO9.e- December, - 12.54 
July, % a January, - 12.76 
August, - 12.87 February, - 13.97 
_ September, 15.42 March, . 14.63 
So that the mean velocity of the wind during one year, (leav- 
ing the direction out of the account,) was about nine miles per 
hour. — atthe mean velocities arrived at in this table were dimin- 
