33 
PART IV. 
REVIEWS AND EXTRACTS. 
1. — Extracts fi-oni the Journal of Agriculture, &c. Quarterly 
numberi?, 8vo., price 6s. 
Page 1. — ^4)1 interesting Acconnt ofiheMeterological Qlxervatio/is of Mr. Aoilf, 
of Edinburgh. — 
Which may not only be useful and instructive to the Agriculturist, for whom 
they were intended, but also to the Horticulturist. He says "the most prom- 
inent feature of the changes that take place in our atmosphere, is the variation 
in its pressure. This variation is indicated in the rise and fall of the mercu- 
rial column of the Barometer. The invention of this instrument, by means 
of which those changes were first shown to exist, was achieved by TorricelU 
in 1643, and it has from that time undergone various alterations and improve- 
ments, till it has arrived at its present state of perfection. The instrument of 
this kind, which in all respects may be considered the best, is the perpen- 
dicular column of mercviry, when the variations in its length are observed by 
a scale of inches and parts. The mean height of the Barometer at the mean 
temperature of the air reduced to the level of the sea, from nine years obser- 
vation was found to be 29,948 inches, and its greatest range 28 to 31 inches. 
In observing the Barometer, the rising or falling of the mercury is to be taken 
as indicating changes in the weather, without regard being paid to the actual 
height of the column. When the Barometer is high and stationary a continu- 
ance of steady and good weather may be expected, corresponding to the 
season of the year; and in general it may be remarked, that the rise is [slow 
and regular when such weather follows. A sudden fall is commonly prog- 
nostic of a gale of wind, whereas, when the fall is slow and regular, rain 
generally ensues. Steady weather is never to be expected when sudden 
changes in the height of the mercury occur; good days may indeed intervene, 
but we cannot depend upon their continuance. In making use of the Baro- 
meter as an indicator of the changes to be expected in the weather, by variations 
in its height, it is of some importance that the mean height, or changeable 
point at the place of observation be found. If the altitude of the place above 
the level of the sea be known, the mean height of the Barometer may be 
found by computation, or simply by subtracting from the mean height at 
the level of the sea, one-tenth of an inch to every eighty-eight feet of altitude. 
But when the height of the place of observation is not known, which will be 
most generally the case, a register of the height of the Barometer should be 
kept, noting every morning and evening at ten o'clock for one year or more ; 
and from these observations the mean height will be obtained by dividing 
their sum by the number of observations : — for example, the sum of one year's 
Vol. 1, No. 1. F 
