May 3, 1873.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
863 
xme, has been referred to. It is a mixture of alcohol, 
.glycerin, and water, generally in the proportions of 
8 parts fluid of alcohol, 3 of glycerin, and 5 of water. 
{To be continued.) 
RECENT PROGRESS IN WEATHER KNOWLEDGE.* 
BY ROBERT H. SCOTT, F.R.S., 
Director of the Meteorological Office. 
{Concluded from, p. 849.) 
A storm may be produced by an increase of pressure as 
well as by a decrease, and some most destructive storms— 
most destructive because they hardly give any warning 
of their approach—are caused by an increase of pressure 
on the eastern shores of the North Sea, while a depression 
is advancing over these islands. The storm of February 6, 
1870, which levelled the harbour works at Wick, belonged 
to this class. Their direction is south-easterly. 
Almost all our storms are related to barometrical de¬ 
pressions, and not to elevations. The reason of this has yet 
to be explained by mathematicians. If, therefore, we knew 
about an advancing depression, the shape (including gradi¬ 
ents in all directions), direction, and rate of motion, and 
whether the disturbance was increasing or diminishing in 
intensity, we should be able to form a fair judgment as to 
what parts of the coast would be most likely to feel a gale, 
and from what points of the compass. There is hardly one 
of these particulars of which we can gain a sufficient know¬ 
ledge until the storm is well upon us, so that the issue of 
warnings to our exposed western and northern coasts will 
ever be a matter of great difficulty and uncertainty. 
As regards the direction of motion of storms, we have 
some progress in knowledge to report. Professor Mohn, 
in his Storm Atlas, has assigned for a few storms the di¬ 
rection and rate of advance, and has shown how both 
these elements are modified as the storm moves across 
Scandinavia into Russia. An English meteorologist, 
Mr. Ley, has also paid attention to the subject; and in 
his recent work, ‘The Laws of the Winds in Western 
Europe,’ has given charts of the mean paths of depres¬ 
sions for certain months of the year. 
Both these investigators refer the direction of motion 
to the distribution and condensation of vapour in the 
atmosphere; and Mr. Ley maintains that the depression 
itself is generated by excessive rainfall, and that its ad¬ 
vance is due to the same cause. We are hardly prepared 
to admit the truth of this statement in its entirety ; the 
area covered by our daily weather reports is too small for 
us to be able to test the matter thoroughly, and but few of 
the foreign stations give either vapour tension or rainfall. 
Moreover, the magnitude of the depressions affords an 
argument against their being simply due to the condensa¬ 
tion of vapour; for on November 22, 1869, barometrical 
readings were reduced to the extent of nearly an inch 
from what they had been on the 21st, over an area of 
about 200,000 square miles. To take a recent instance, 
on the 20th of January, the deficit of atmospherical pres¬ 
sure amounted to about ^th of its total amount over the 
United Kingdom, the readings ranging between 28*0 and 
28'5, instead of between 29'5 and 30 - 0. 
We know that the direction of motion is ruled very 
much by the position of the areas of high pressure, which 
are of considerable superficial extent, and, as a rule, are 
not subject to much motion of translation. The depres¬ 
sions appear to skirt round these areas of high pressure, 
and not to advance into them. As an illustration of the 
effects of an area of high pressure on our weather, it may 
be remarked that one of the worst signs for us of the 
danger of a south-westerly gale is to find the barometer 
over the south of Franee high and rising. 
The simplest idea of the general motion of these areas 
of depression is, that they follow each other in the main 
* Abstract of a Lecture delivered at the Royal Institu¬ 
tion of Great Britain, Friday, February 14th, 1873. 
stream of air, which sweeps round the permanent area of 
low pressure near Iceland, much in the same way as 
eddies in a running stream. Many of the depressions 
appear to be modified in their character by the contour of 
the land. More than once a storm which has apparently 
struck the land about Valencia, travelled northwards 
until it found an opening in the coast-line, such as Donegal 
Bay, and then crossed to the Irish Sea, or else skirted 
round Ireland and crossed the Lowlands of Scotland. 
In some cases which we are as yet quite unable to anti¬ 
cipate the disturbance changes the direction of its motion 
entirely, and returns for a time on its former path. This 
was in a marked way the case with the storm of April 21, 
1872, which came down over Ireland, between Valencia 
and Armagh, swept round along the north coast of France 
up to Havre, recoiled and passed north of Portland and 
Falmouth to the south of Ireland, and eventually tra¬ 
velled out to sea across Ireland, nearly in the direction 
along which it had arrived. Such a storm as this sets us 
quite astray, and makes our warnings quite wrong. An¬ 
other circumstance which complicates the study of storms 
is, that depressions increase or decrease in their intensity, 
and of the rate of this change we are quite ignorant. 
Of storms which are mainly due to a rise of pressure, 
one, in February, 1871, may be selected for an illustra¬ 
tion. This depression advanced from the westward, but 
hardly assumed the character of a storm until the morning 
of the 10th of February, when its centre lay over the 
north of England. Now, between the 9th and 10th the 
barometer over the North Sea had risen briskly, so that 
when the new depression came it found the conditions fa¬ 
vourable to high gradients and south-east gales on its 
eastern side. Its appearance was quite unexpected ; for 
even at 6 p.m. on the 9th there were little signs of it, and, 
moreover, its force at 8 a.m. on the 10th was moderate 
compared with its fury later in the day. The centre 
finally passed over London, and the whole phenomenon 
passed on to the Continent, where it is untraceable, in 
consequence of the absence of reports, owing to the war. 
Easterly gales are, on the whole, difficult to foresee ; 
they come with little warning ; and this is not solely 
attributable to the deficiency of information from Eastern 
Europe, for since we have received warnings from that 
region, we have hardly had an instance of a warning 
which preceded the gale. In most instances the easterly 
storm was on the north side of a depression travelling 
eastwards, and began first at our western stations. Such 
was the storm of Sunday, Feb. 2, which set in as an east 
gale at Pembroke, and subsequently extended to stations 
lying to the eastward. Some of these easterly storms do 
apparently advance from the eastward, and to this class 
belongs the fearful storm of Nov. 12-13, in the Baltic. 
The ravages of this storm were mainly caused by the fact, 
that a continuance of westerly winds had dammed back 
the water at the Skager Rack, and then, when the wind 
chopped round to east, the narrow channels between the 
Danish Islands could not discharge the water quickly 
enough. The unavoidable result was an inundation. 
What are now the signs of a storm, and when do we 
issue warnings ? We are perforce driven to use the baro¬ 
meter mainly, as it is an instrument more closely related 
to the direction and force of the wind than the thermo¬ 
meter, and one whose daily range is triflingbut if we 
trust it alone, we shall hardly ever be certain about a 
storm, and the thermometer will not help us much. We 
have other signs, such as shifts in the direction, of the 
wind, increase of sea, and all the manifold local indications 
given by the character of clouds and the transparency, etc., 
of the air, invaluable as collateral information, but re¬ 
quiring a practised eye to discern them. 
If it were possible to place the meteorological office, 
with its present telegraphic facilities, on the west coast of 
Ireland, we might fairly hope to foretell five-sixths of the 
storms which strike us. On two separate occasions the 
lecturer, being in that district knew perfectly well from 
the look of the sky that a storm was coming some hours 
