APPENDIX I), (pp. 539—548). 



DESCRIPTION OP THE TYPHOON ENCOUNTERED IN THE CHINESE SEAS, BY 

 H. I. R. M.'s FRIGATE NOVARA, ON THE 18th AND 19th AUGUST, 1858. 



The path of the typhoon has been deduced from comparison with the 

 readings of the barometer, with which it corresponds pretty accurately, if 

 due allowance be made for the fact, that in determining it the various 

 directions in which the line of centres runs must be calculated on the 

 supposition that the orbit of the cyclone is circular, which it is not 

 in reality, since at any considerable distance from the centre it must be 

 elliptical. Hence it is apparent that the rate of velocity of the cyclone 

 in advancing along its path follows no fixed law, whereas some such re- 

 gularity undoubtedly exists among the masses of air encountered by the 

 cyclone. Hence too the errors thus made in specifying the direction of 

 the wind become of considerable importance in this connection, more espe- 

 cially in the event of the place of observation being at any distance 

 from the centre, or that the path of the cyclone forms a sharp angle 

 when wheeling round. Moreover, as actually experienced, the path of 

 the tj^Dhoon would lie more near the line of the points of observation 

 than a sketch founded upon such observations would indicate, and than 

 a general comparison of the paths of cyclones founded upon the theory 

 of their gyratory motion would substantiate, except in those cases where 

 the observer has been directly in the path of the cyclone. 



In our case the absolute distances, as specified in the annexed table 

 (see p. 490) of fifteen difierent stations taken during the three days 

 during which the cyclone and its premonitory and subsequent symptoms 

 lasted, are only assumed, because simultaneous observations of the vary- 

 ing directions of the wind could not be taken at various points of the 

 course of the cyclone, and in so far may be inaccurate, although the 

 relative distances might possibly be tolerably correct. 



The observations as to the direction of the wind at noon of the 18th 

 August and at the ensuing midnight, give results contradictory to the 



