Calcutta and many districts of Bengal were ravaged by a very severe cyclonic storm on 5 October 1864 taking a very heavy toll of life and causing extensive damage to ships and property. A high percentage of the lives lost was due to the outbreak of disease in the aftermath of the cyclone.

A “Report on the Calcutta Cyclone of the 5th October 1864” was prepared by Lieut-Col James Eardley Gastrell and Henry Francis Blanford for the Government of Bengal by order of the Lieutant Governor. Blanford was at that time the Secretary of what was called the Meteorological Committee of Calcutta. Later in 1875 he was appointed the Imperial Meteorological Reporter when the India Meteorological Department was established.

This voluminous report of over 200 pages reconstructed the entire meteorological scenario prior to, during and after the cyclone, using data from 16 land stations and 10 ships, eyewitness reports, personal logs and registers. It also documented the loss of human life (which was estimated as 48, 685) and damage to property due to the storm.

Additionally, the committee made a very scientific significant contribution by studying 52 previous cyclones recorded during the years 1737 to 1865, on the basis of which it prepared the following summary regarding the frequency and tracks of cyclones in the Bay of Bengal, which I quote from its report:

I.—Cyclones occur chiefly at the periods of changing monsoon.

II.—That they are more numerous at the close of the south-west monsoon [October, November] than at its beginning [May, June].

III.—That they sometimes, but rarely, occur in the north of the Bay and Bengal during the south-west monsoon months [July, August, September]; never in the south.

IV.—That they sometimes, but rarely, occur in the extreme south of the Bay and between Ceylon and north latitude 5° in the north-east monsoon months, [December, January, March]; never in the north of the Bay.

V.—That at the change of north-east to south-west monsoon they occur most frequently in April in the south of the Bay; in May about equally in all parts of the Bay; in June chiefly [or only ?] in the north of the Bay.

VI.—That at the change of south-west to north-east monsoon the October storms are most frequent in the north of the Bay. In November they are rare in the north, common in the south of the Bay.

VII.—Storms originating in the north of the Bay usually travel between north by west and north-west by west.

VIII.—Storms originating near the Andaman Islands, (excluding those of the Andaman sea,) travel between north north-west and west.

IX.—Those originating in the south of the Bay travel usually to west, or a little to north of west.

What is really striking is that the above findings were drawn at a time when the number of observatories was so small, when data had to be obtained by post, and when there were no radars, satellites or computers. And what’s more, they still hold good! Over three centuries, the climate of the Bay of Bengal has not changed! 

The Gastrell-Blanford Report of 1866 is available in its entirety on Google Books. To read online or download it as a pdf file, click on the thumbnail below: