1869.] Mr. H. F. Blanford on the Origin of a Cyclone. 477 



Botelbhoe/ ' Timoor Shah/ and ' Gauntlet ' that the wind was beginning 

 to circulate around the area of greatest depression and of variable winds. 

 The first of these ships, whose course was northward and on the east of 

 the area in question, had a moderate breeze veering from N.E. to E. with 

 heavy squalls ; the second, moving slowly up on the west of the area, had 

 northerly freshening breezes and an overcast sky with rain and a heavy S.W. 

 swell. The 'Gauntlet/ at 200 to 250 miles to thesouth,hadthewindatW.N.W, 

 with hard rain-squalls. There is, however, no evidence of the w r ind having 

 attained to anything like hurricane violence until the following day. 



On the 27th the barometric pressure remained much the same as on the 

 previous day over the greater part of our area. The barometric difference 

 between Chittagong and Akyab amounted to about 0'05 inch, and to an 

 equal amount between the latter place and Port Blair. At 70 miles to the 

 west of the Andamans the barometer of the ' J. C. Botelbhoe' stood 0*1 

 inch lower ; but the lowest pressure recorded on this day was experienced by 

 the 'Gauntlet' in lat. 7° 5' at about 100 miles due west of the Nicobars. 

 The reading of this ship's barometer was 29"562, or 0'29 less than at 

 Port Blair, and 0'22 less than on the Equator to the south, 4 less than 

 at Calcutta and Dacca, and nearly 0'36 less than at Madras. There can 

 be little doubt that to the west of the Nicobars there had beeen a rapid 

 fall during the two previous days. On the morning of the 24th the * Jam- 

 setjee Cursetjee Botelbhoe ' had passed within 40 miles of the ' Gauntlet's' 

 noon position of the 27th, her barometer standing at 29*772 at noon of 

 the 25th ; when her barometric reading was nearly the same, she was at a 

 distance of little more than a degree to the north. 



The form of the area of depression would seem to have been a very 

 elongated ellipse, or a trough, stretching from south to north, and of no 

 great width. That the rise was rapid to the eastward, we have evidence 

 in the observations of the * Prince Arthur ' and the ' Jamsetjee Cursetjee 

 Botelbhoe.' On the other hand, the barometer of the ' Comorin,' at 200 

 miles to the west of the Little Andaman, showed a reduced reading of not 

 less than 29*9. It is true that the barometer of this ship has not been 

 compared, and it is not improbable that its readings are somewhat high, but 

 that its error is so great as to produce the whole of the apparent difference of 

 its reading and that of the ' J. C. Botelbhoe' barometer is highly improbable. 



In Bengal the winds were from the N. and N.W. (the usual directions 

 during the cold-weather months), and N.E. down the coast of Orissa and 

 the Carnatic. Over the north of the bay, as on the previous day, the pre- 

 valent directions were N.E. and E.N.E. ('Winchester/ ' St. Marnock/ 

 ' Leonie/ ' Mongolia '). But at Akyab the wind was southerly, and at 

 Port Blair veering to S.E. The W.N.W. winds that had hitherto pre- 

 vailed between the line and 5° or 6° N. lat. were now drawing round to 

 the place of maximum depression, since the ' Astracan/ coming up from 

 the Equator across this belt on the 27th and the following day, experienced 

 strong breezes with hard squalls from W.S.W., the sky overcast with cirro- 



