ON THE REDUCTION OF METEOROLOGICAL OBSERVATIONS. 73 
rise to the end of the projected series, may be taken as the general character 
of the curves; in which the diurnal maxima and minima are for the most 
part conspicuously traceable, and which, when allowed for, equalize several 
of the curves nearly into regularly sloping lines, with a slight general con- 
vexity. This is especially the case with Brussels, Greenwich, London, Ash- 
urst, and Oxford; the curve for Brussels being decidedly the smoothest of the 
whole series. In Markree and Cambridge absolute maxima occur at the 
14th hour, which is followed at Markree by a very gentle and continued 
depression ; while at Cambridge, after descending to a pretty abrupt minimum 
(at 17 hours), the rising tendency is resumed and carried out to the end. 
At Halifax the rise is continued till between 16 and 17 hours, when an abso- 
lute maximum occurs, followed by an undulating level. At Geneva also 
there is an absolute though slight maximum from 13 to 14 hours, followed 
by a very slightly undulating level to the end. At Kremsmiinster the early 
minimum (as is also the case at Geneva) is more marked and prolonged than 
can be referred to the action of the diurnal oscillation. In fact the Krems- 
minster curve consists of two unequal portions like a vibrating string, having 
a node at the 15th hour, the earlier portion being concave, the later convex 
upwards; the deflexions in both, however, being small, viz. 0°03 inch and 
0°05. 
_ Hanover is again peculiar; as far as the 17th hour its curve follows the 
same law of gentle and undulating rise; but here a sudden irregular action 
commences, indicated by a great protuberance caused by a rapid rise of 0°10 
inch toa maximum at 8" 36™, sinking thence to a minimum at the 22nd hour, 
and again rising to the end. 
From the type of all these curves that of Turin differs entirely. It com- 
mences by a gentle descent to a slight minimum at 2" 36™, from which it 
nearly recovers by an undulating rise as far as 5" 36™, when it takesa sudden 
plunge down of 0:086 inch to an abrupt minimum at 6" 45"; whence it im- 
mediately recovers, and in the three next hours ascends through 0°132 in. 
to a maximum at 9" 45™, then descends unsteadily through 0:067 inch to 
another minimum; after which follows a gentle rise to the end of the term. 
Nothing can place in a clearer light the action of the Alpine chain in inter- 
cepting a small wave, of which the undulations might be confined chiefly to 
the lower strata (since nothing prevents the atmospheric strata from being 
very unequally disturbed, as we see in the fluctuations of superposed liquids). 
The curve for Cadiz commences, like that of Turin, with a gentle descent, 
and, like it, has a slight minimum at 25 36™, whence it recovers, not as at 
Turin, by violent starts and falls, but by a very gradual and easy slope up to 
12 13™, when it again descends. From 13"°36™ to 155 42™, however, we 
are reminded by a protuberance in the descending line, of the feature already 
signalized as a peculiarity of this station on former occasions. 
Hitherto we have foreborne to mention the Edinburgh curve, which exhi- 
bits a strange anomaly, such as neither the course of the changes at Markree 
or Halifax would lead us to expect, and which, if it do not arise from some 
error of reading affecting the first 6 hours, goes to place in a strong light the 
capricious suddenness of the barometric changes at this station, of which we 
have already seen instances. 
The Edinburgh curve commences, like the other British and many of the 
continental ones, with a slight fall to a minimum; anticipatory in this case 
of the regular diurnal minimum, viz. at 1"24™; thence it rises gently enough 
(through 0:059 in.) as far as 6 24™, when on a sudden it starts up, rising in 
the next 2 hours through 0°244 in., after which it maintains this increased 
level with only a very trifling variation up to the end of the series. 
