526 Proceedings of the Royal Society 
ing that storm, and merely substituting American dates and places 
for British. 
The chart of 15th showed that the cold west wind, which was 
first felt in Texas at 9 p.m. of the 13th, and was at first travelling 
faster in the south than the north, had swept the whole country 
as far east as St Johns in South Carolina, and northwards as far 
as Oswego at the east end of Lake Ontario. The line of minimum 
barometer was then nearly straight from St Johns to Oswego, cold 
winds prevailing on the west, and warm on the east side of it. 
The author then drew attention to the phenomena of calms that 
appear in the front and rear of all the American storms, as well as 
our own. The calms stretching southwards from Toronto, on the 
night of the 13th March, advanced eastwards at the rate of 10 to 
12 degrees of longitude a day. On the morning of the 15th the 
calms were east of Nova Scotia. At the very same time another 
series of calms was produced on the west from Texas north to 
the west end of Lake Superior. Frost now visits Texas, where 
thirty-four hours before the thermometer stood at 82° in the shade. 
This series of calms was the forerunner of another and more severe 
storm then to the west of them. On the morning of the 16th the 
central axis of the calms was over the 85th longitude, having 
again advanced 10 to 12 degrees in twenty-four hours. The 
calms, then seen where there were a multiplicity of stations, 
showed that they were of the form of a pyramid, rounded at the 
top, but wide at the base. Along the shores of the Gulf of Mexico 
the region of calms was at least 700 miles broad, but not more than 
200 miles on the Lakes. The advance eastwards of these calms 
from day to day, with the storm to the west of them, was then 
traced. 
The storm on the west of the calms of the 16th was traced out. 
Charts were exhibited of the morning of the 18th and night of the 
18th, showing its progress from west to east over the States, and 
that the west wind advanced faster over the Southern States than 
the Northern. As a consequence, the minimum line of barometer 
was largely bent over the Eastern States, stretching from north- 
west to south-east — this direction being exactly reversed from that 
of the morning of the 15th March. 
The author then pointed out the relation which the winds to the 
