ON THE REDUCTION OF METEOROLOGICAL OBSERVATIONS. 75 
completely observed), both of a gentle character. The absolute culmination 
occurs at 4" 30™ (Sept. 21), and the total observed range small (0*172 inch). 
The Halifax series (which is complete, including 36 hours) exhibits the 
Wave in progress of ascent from 5"30™ a.m. to 5" 30™ p.m. of the 21st; during 
which 12 hours the mercury had risen 0°278 inch. At this epoch (55 30™) I 
place the first culmination, which is, in fact, the highest of a series of low 
undulations. The second takes place at 8°30", but is of so flattened and 
obsolete a character that it hardly deserves to be called so, and is rather a 
low convexity interposed between the first and third, which occurs at 105 94™, 
and is more marked, though not strongly, and at a lower level by 0033 inch 
than the first. From this the curve descends very regularly to the end. Total 
observed range = 0°348 inch. 
At Oxford the first culmination is 5520". It is a sharp and sudden pin- 
nacle on the upward general slope of the curve of about 0°07 inch in height 
on 4 base of 2 hours. From its subsidence at 6" 20™, the curve continues 
to rise for three hours more, till it attains a second maximum from 9" 30™ to 
105 30™, which places the second culmination at 10 hours. The form of this 
culmination is an obtuse bulge extending over the three hours from 8 30™ 
to 11530", and is followed by a dead level leading to a shoulder or quick 
slope at 15"30™, and which is the last representative of our third culini- 
nation, which seems to have died out or thinned off in the progress of the 
wave. 
At London the ascent of the wave continues till 6"18™, which is the epoch 
of the first culmination, indicated by a great bulge in the upward slope (as 
at Oxford) of 0°07 inch in height and 3 hours in breadth. The second cul- 
mination occurs at 10" 18™, and is here the higher of the two, by a very tri- 
fling difference (0°007 inch), and from it the descent of the wave commences 
and continues uninterrupted. 
Greenwich, though so near London, has the epoch of the first culmination 
an hour later; that of the second coincident, and also (0°007 inch) higher 
than the first. Both too are sharper. The descent of the curve is also some- 
what more undulating than for London. 
Passing from the British to the continental curves, we are at once presented 
with a marked contrast in respect of smoothness. The Brussels curve offers 
a very uniform and even convexity. The distinction of the culminations is 
obliterated, and an absolute maximum at 13 hours is alone observable. At 
this station the total range of ascent observed (during 19 hours) was 0:957 
inch, and that of descent (during 17 hours) = 0°289. The curves for 
Alost and Louvain appear in all respects similar, but both their vertices are 
wanting. Passing now to Geneva, we find the ascent of the wave observed 
during the first 23 hours, and the descent during only the remaining 13 
liours of the total series of 36 hours. The absolute culmination observed 
occurs at 21 hours, or at 9 A.M. of September 22, and no distinction of what 
have been called above the first, second and third culminations is to be made. 
But in the sloping ascent of the wave 10 hours antecedent to the culmina- 
tion, is a very remarkable bulge, extending over the interval from 9 hours to 
18 hours, which, as it appears also in the Turin and Parnia curves, deserves 
notice. The whole ascent appears in the Geneva curve, and the minimum 
or trough of the preceding wave occurs at 1 hour; the total range of ascent 
being 0343 inch, occupying 20 hours, being preceded by 3 hours of unde- 
cided fluctuation. 
At Kremsmiiinster also the ascent of the wave, if not from the absolute 
minimum preceding, at least from a relative minimum but little elevated above 
it, has been observed. The true culmination took place at 21" 25™, and the 
