94 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



Mr. Bland ford's article, speaking of the severe cyclonic storms, 

 be states that the highest wind that has yet been registered 

 in Calcutta gave a pressure of fifty pounds to the square 

 foot; but this was a storm of no remarkable violence, and 

 which did little injury in that city. There is a prevalent 

 impression that cyclonic storms have been more frequent of 

 late years than formerly ; but this idea is more likely to be 

 a consequence of the increased attention given to the sub- 

 ject, since in recent times every storm that occurs is fully 

 noticed, with all procurable data, in the meteorological re- 

 ports. JProc. Asiatic Soc. of Bengal, 1873, 178. 



THE TORNADO OF MAY 22, 1873. 



The very thorough report of Sergeant Mcintosh, of the 

 Signal Service, on the severe tornado experienced in Iowa 

 and Illinois on May 22, 1873, affords us the following facts, 

 condensed from the forty pages of detailed observations 

 given by him : 



An area of low barometer existed in the Mississippi and 

 Missouri valleys from the 20th to the 22d of May, moving 

 very slowly northward. This induced a southerly warm 

 current over a large portion of the interior of the continent. 

 The result was a series of violent local storms, generally ac- 

 companied by hail, and always by lightning. They reached a 

 climax in the tornado which is the subject of this paper. 



A lmoje dark cloud covered an area of at least thirtv miles 

 in diameter. Under the southwest edge of this cloud was 

 observed a perfectly opaque, funnel-shaped appearance, reach- 

 ing from the ground to the clouds ; toward its base the wind, 

 in spirals, rushed violently from all sides, overthrowing what- 

 ever opposed its progress; toward its summit, where it dis- 

 appeared in an overhanging horizontal cloud, long streaks of 

 clouds rushed, in spirals, from all directions. Under the re- 

 mainder of the main cloud, which lay chiefly to the northwest 

 of the rising: column, there ragred a tremendous storm of hail 

 and rain, accompanied by incessant electrical phenomena. 

 The summit of the dark cloud is computed to have been 

 fifteen miles above the earth's surface, its horizontal diame- 

 ter being at least thirty miles, as before stated. The under 

 surface of the cloud was less than three miles in altitude at 

 one point, and at another point scarcely half a mile. The 



