529 
of Edinburgh , Session 1868-69. 
of these States (a mere spect on the charts) than the 100,000,000 
of tons of coals that Great Britain raises in a year. The vapour, 
as it becomes condensed in rains, converts the atmosphere into a 
vast caloric engine, and produces vast effects. Twenty-five miles 
of calms on the west side of the calm region are every hour con- 
verted into easterly winds, which blow towards the line of minimum 
barometer, and 25 miles of calms are produced every hour on the 
east side ; and besides, the air, as seen in chart of 16th March, is 
tossed over the calms, as an upper current from the west, and as it 
cools by radiation, descends and supplies the cold and dry winds 
that blow in the rear of the minimum line of barometer on the 
west side of the previous storm. 
The rate at which the calms are propagated along the latitudes 
is the true index of the rate of a storm’s progress. Whatever may 
be the particular character of the disturbance within, the calms on 
the east and on the west contain the whole body of the storm 
within their bounds. Their rate of propagation is the true rate 
of that of the disturbances within. With all deference to Espy, 
storms must be propagated faster along the south ; for so long as 
the central axis of the calms is meridional, it must move more 
rapidly in the south, for the simple reason that the meridians are 
wider there. 
3. On the Boulder-Clay of Europe. By D. Milne-Home, Esq. 
It was explained that this deposit, known in Scotland as Till or 
Boulder-Clay, prevails also in Ireland, the Isle of Man, England 
(north of the Thames), Denmark, and Sweden, though much less 
abundantly in these last countries. It exists also in the Hudson’s 
Bay districts, and at the south extremity of South America. 
It had been a subject of perplexity to geologists ever since 
attention was drawn to it, fifty years ago, by Sir James Hall of 
Dunglass,- whose papers are in the Transactions of this Society. 
About the year 1840 a theory was started to account for the 
boulder-clay, and other phenomena allowed to be connected with 
it, by the action of glaciers. 
At first, local glaciers were proposed ; but latterly there seemed 
to be a disposition among Scotch geologists to adopt the startling 
