80 Proceedings of the Royal Society 
sphere, where the land at this season is colder than the surround- 
ing sea, brings about a higher pressure for May ; but the influence 
of land over regions heated more immediately by the sun brings 
about a lower pressure — interesting examples of which are seen 
in the distribution of the differences of pressure over India, 
the Malayan Archipelago, the Mediterranean, Black, and Caspian 
Seas. In many such cases the lines follow more or less closely 
the contour of the coasts, or, more strictly speaking, the lines 
resembling the contours lay some distance to eastwards, so that 
there is a less diminution over those seas than over the land 
surrounding them. Nearly the whole of Asia shows a very large 
deficiency of pressure — the Arctic regions to the north of Europe 
and North America the maximum excess of pressure. It is to 
the position of Great Britain, with reference to the deficiency 
of pressure on the one hand, and the excess on the other, that 
the east winds at this time of the year are due. Those easterly 
winds prevail over the whole of northern Europe, as far south 
as a line drawn from Madrid in a north-easterly direction, and 
passing through Geneva, Munich, &c. To the south of that 
line the diminution of pressure is less, and over that region 
the excess of wind is, not easterly, but southerly. Crossing the 
Mediterranean, and advancing on Africa, we approach another 
region of lower pressure ; and towards that region north-easterly 
winds again prevail, as at Malta, Algeria, &c. The effect of 
these different winds upon the rainfall is very decided. Southerly 
winds from the Mediterranean result in heavy rainfall over France 
and Central Europe in the month of May. 
The effect of those east winds upon diseases is very great. 
They derange our nervous system, and bring about a series of com- 
plaints, physical and mental, an inquiry into which would form an 
interesting and important subject of investigation. 
3. On Vortex Motion. By Sir William Thomson. 
The following Gentlemen were elected Fellows of the 
Society : — 
Andrew Pritchard, M.R.I., Author of a work on Infusoria, Highbury, 
London. 
