1883.] occurred at Dacca on April 7th, 1888. 205 



yards in breadth in which was concealed a Miihammadan village. All 

 the trees on the east side of the track of the tempest were lying directed 

 towards the river in a northerly direction, all on the west side were 

 directed southwards, inland, away from the river. The former had 

 been broken or uprooted by the advancing lateral radius, the latter by 

 the retrograding lateral radius. In the centre of the track, where they 

 had been exposed to the anterior radius, and afterwards to the posterior 

 radius as well as to the inner lateral radii, nothing but stumps were 

 left ; for it is clear that, while all objects outside the lines MN and OP (in 

 Fig. A., PI. XXVII) will be exposed to only one wind force, an advancing 

 one in the case of OP, or a retrograding one in that of MN, those within 

 those lines will be exposed to three out of the four wind forces in action. 

 Thus, an object situated in the line RS will be first thrown to the left by 

 the wind forces after they have passed the line CE, then subjected to a 

 retrograde force on the line CK, and will afterwards be tossed to the 

 right by the wind forces approaching CF. It was thus that the tornado 

 ground its way through the Kawab's palace and through the masonry 

 houses between his palace and the main street of the town. 



For these reasons, when the tornado is passing over masonry build- 

 ings, it will appear as if most of the destruction near the centre of the 

 track had been done by a wind blowing from right to left, because the 

 wind forces at right angles to CE, the anterior radius, are the first to 

 come in contact with them. They are immediately thrown down to the 

 left and remain there undisturbed by the subsequent rotatory winds 

 which pass over them. So it is with plantain trees, which do not snap 

 across, but bend and break and lie down flat, retaining their connection 

 with the root by a short stump. But with hard wood trees, and with 

 kutcha huts and furniture, it is different. They are first carried to the 

 left by the wind force near the anterior radius, and afterwards lifted and 

 carried from left to right by the forces on the posterior radius. Thus, 

 it was not uncommon for the roof of A's house to be carried into B's 

 compound, and immediately afterwards B's roof to be lifted and deposit- 

 ed in A's compound. So in the Nawab's house an almirah in one room 

 was carried through a doorway into another room, and from the latter 

 a writing-table was carried through another doorway into the former 

 room. These interchanges only take place near the centre of the track. 



The tornado of the 7th of April began its destructive course at the 

 extreme west end of the Municipal limits. Its exact method of com- 

 mencement will be described further on. Here the houses are built on 

 an old river bank, the bank of the old bed of the Buriganga, which at 

 this season is here a mere khal. This old river bank is continuous in a 

 nearly straight line with the present bed of the Buriganga, which now 

 27 



