Tropical and Extra-tropical Cyclones. 



23 



The shape of Japanese cyclones is usually oval ; but well-defined 

 typhoons are more nearly circular than the ordinary depressions of 

 that country. The latter are, however, as a rule, far more pronounced 

 ovals than in Europe. As typhoons move into higher latitudes, they 

 certainly tend to become larger, more irregular in shape, and to move 

 with greater rapidity. The centre is almost always more or less 

 displaced, but the longer diameter tends in a marked degree to lie 

 nearly parallel to the line of propagation. 



Secondaries seem to be rare on the sides of the primaries ; but the 

 latter have the same reluctance to traverse land, and the same 

 tendency to follow one another along the same path, which are found 

 so frequently in European cyclones. 



The velocity of translation is greater than in the Philippines ; but 

 the July typhoons usually move more slowly than those in August or 

 .September. 



Mr. Knipping thinks from observations on the upper clouds that 

 the height of some typhoons does not exceed three-quarters of a mile, 

 or about 4000 feet ; but the author considers this estimate far too 

 low. 



The wind is usually less incurved in front than in rear of the 

 centre ; and at some distance in front, with a S.E. wind, the centre 

 may bear S. This is a very important point with reference to 

 handling ships, but cannot be discussed here for want of sufficient 

 information. It is, however, quite certain that though the baro- 

 meter may have begun to fall, a ship may not really be within the 

 sphere of the typhoon. 



Much information could not be got on the movements of the upper 

 clouds. Some of the observations at Nagasaki are very discrepant. 



The author believes, however, that there is not the slightest doubt 

 that the general circulation of a typhoon is exactly similar to that in 

 an extra- tropical cyclone, for Mr. Harries (' Quarterly Journal of the 

 RoyalMeteorological Society,' vol. 12, p. 10) has traced a typhoon from 

 the Philippines across the Pacific and the United States into Europe. 

 This, like all other long-lived cyclones, received accessions of inten- 

 sity from time to time by fusion with other cyclones which had 

 formed outside the tropics ; and it is inconceivable that two eddies, 

 circulating on different systems, could coalesce without destroying one 

 another. Cyclones are supposed to have the same general circulation, 

 or to circulate on the same system, when the whole body of the storm 

 circulates in the same manner — in-going counter-clockwise below, 

 tangential to the isobars at low levels, outgoing at the highest altitudes. 

 Two such cyclones, near one another, can and do easily coalesce ; but 

 if the upper currents in a typhoon were essentially different from 

 those in extra-tropical cyclones, two adjacent cyclones could not 

 coalesce without destroying each other. Cyclones south of the 



