of Edinburgh, Session 1868-69. 
525 
2. On the Rectangular Current Theory of Storms, illustrated 
by two Storms which passed over the United States, from 
the 13th to 19th March 1869. By Robert Russell, Esq. 
The author’s former views on American storms were first alluded 
to — i.e., that the phenomena could only be accounted for on the 
supposition that there were two distinct currents. Instead of these 
being parallel, they were more nearly at right angles to each other. 
The southerly current on the eastern axis of storms brought up 
heat and moisture from the Gulf of Mexico, causing the baro- 
meters to fall. The west or north-west wind, on the other hand, 
cleared the southerly current away, causing the temperature every- 
where to fall and the barometer to rise. 
The storms under review were then examined by M. Le Yerrier’s 
mode of laying down isobarometric lines on charts, but for ever} 7 
tenth of an inch of pressure instead of two-tentlis. The southerly 
current was shown to have distinct lines of contour and order from 
the other — the west or north-west at right angles to it. 
The minimum line of the barometer where the currents meet, or 
where the west flowed into the southerly, was described and pointed 
out ; the barometers obtaining their lowest reading, and thermo- 
meters their highest on that line, on any latitude, from the Lakes 
to the Gulf of Mexico. As formerly defined, in the Proceedings 
of this Society, “ the latitudinal line of minimum barometer repre- 
sents that space where the air, from the surface of the earth to the 
top of the atmosphere, is warmest on any latitude, and consequently 
lightest.” 
The charts of 13th and 14th March 1859 were first exhibited, 
showing that thunder storms with rains prevailed up the Mississippi 
valley, as far north as the southern border of the State of Michigan. 
At the same time a severe snowstorm from the north-east prevailed 
over Minnesota, Northern Wisconsin, and Northern Michigan— -a 
foot of snow falling over a large extent of country. The line of 
minimum barometer was greatly curved, or, what is the same thing, 
stretching from south-east to north-west in its northern part. The 
remarkable analogy between the main phenomena of this storm 
and that of the “ Royal Charter” storm of 1859, was pointed out by 
the author reading a passage which he had formerly written regard- 
