1895 - 96 .] 
Chairman's Opening Address. 
5 
simple Reaction-Time for Sight, Hearing, and Touch. The re- 
action-times, he has found, differ from those of certain German 
observers. That for sight was mostly between 0*20 and 022 of a 
second ; for hearing, from 0*15 to 0T6 of a second ; for touch, 
from 0T416 to 0T906 of a second. 
Dr John Murray and Mr Robert Irvine have discussed the 
occurrence of Oxides of Manganese in Fresh and Sea Water, with 
special reference to the lochs of the West of Scotland. They point 
out that manganese in combination with silica is present in many 
of the rocks within the drainage areas of those lochs, and that this, 
in all probability, is the source of the dioxide of manganese present 
in marine deposits. The silicates containing manganese are broken 
up, and the manganese converted into a bi-carbonate, which is 
eventually deposited as manganese dioxide. 
Mr John Aitken, in addition to two interesting papers on the 
Hazing Effects of Atmospheric Dust, and on Breath Figures, gave 
an interesting communication on the number of dust particles in 
the atmosphere of certain places in Great Britain and on the 
Continent. He pointed out the remarkable fact that at Kingair- 
loch and other places, when the sky was entirely clouded, the 
number of dust particles showed no tendency to rise as the day 
advanced ; with a clear sky, however, the number of particles 
increased, and generally in proportion to the amount of clear sky. 
Much of the dust is so fine that it will scarcely settle of itself, but 
the deposition of vapour on the particles causes them to form 
rain-drops and fall, and so the air is purified. 
Dr Buchan, in an elaborate paper, has insisted that the prevail- 
ing winds of the globe, in their direct and indirect effects, are the 
most powerful agents concerned in oceanic circulation. They 
originate and maintain the surface-currents of the ocean ; and the 
influence of these currents is, through friction, felt to a depth of 
probably several hundred fathoms. In intertropical regions the 
prevailing trade-winds drive the surface-currents westwards 
towards the western shores of the continents, and there, accord- 
ingly, a greater depth of warm water is found in the upper layers 
of the ocean than elsewhere. Except where the rainfall is 
abnormally heavy, this water is not only very warm but has a 
higher salinity than the general average of the ocean. It is one of 
