62 
Proceedings of Royal Society of Edinburgh. [sess. 
Barographic Record in the Vicinity of a Tornado. By- 
John Anderson. Communicated by Dr Buchan. (With 
a Plate.) 
(Read June 2, 1890.) 
The fluctuation shown by the barographic record occurred imme- 
diately after 6 p.m., at the time of the passage of the tornado of 
Thursday, March 27, 1890, near Owensboro, Davies County, 
Kentucky. The distance of the barograph from the nearest point 
of the tornado can be approximated by the evidences of damage 
the tornado left, and did not exceed a mile and a quarter or a mile 
and a half. At this distance to the south-east of Owensboro there 
is a ridge 150 or 200 feet high, and a large brick house on top was 
unroofed and partially demolished. This is the first evidence of 
destruction in the vicinity of Owensboro, but previous to this the 
noise of the approaching tornado was plainly audible to persons on 
the streets of the town. Until reaching the ridge above mentioned, 
the tornado appears to have passed in the air, accompanied by a 
roaring sound, without doing any damage in its passage. From a 
point about twelve miles to the south-west a tornado passed over 
the latter city two hours later. The rate of progress of the cyclonic 
area of low pressure, as shown by the signal service map, was forty 
miles an hour. On the same day a parallel tornado passed about 
thirty miles to the south of Owensboro, near south Carrolton. 
There was none to the northwards. 
The sudden dip in the barometric curve at 6 p.m. of March 27th 
is shown on the accompanying Plate. Though the centre of the 
tornado was from a mile and a quarter to a mile and a half distant, 
yet the barometer fell suddenly about the tenth of an inch, and 
immediately thereafter rose as suddenly to a point nearly two- 
hundredths of an inch higher than the point from which it fell. 
This observation, which is new to science, gives the explanation 
of the wrecking of buildings by tornados as by an explosive force 
within the buildings. The sudden lowering of the pressure outside, 
which must greatly exceed the tenth of an inch near the centre of 
the tornado, is amply sufficient to account for the fearful energy 
developed in these tempests. 
