Stationary cyclones occur under favorable conditions. At least that name has been applied to columns of hot air streaming up from a fixed base, more or less circular. Every island in the ocean generates such a vortex on a clear, hot summer day, since its temperature far exceeds that of the surrounding water. All day long this uprush continues whatever be the humidity. And if the soil slopes upward steeply, the vortex is so much the stronger, particularly if the island be in a calm region. Above such a tract the gulls and vultures, and possibly even man, might soar all day without motive power. This condition and its interesting possibility deserve investigation. Cyclones may occur at any season, but in general they are most abundant when the greatest temperature disturbances occur. The relative frequency of tropical cyclones for various localities and for the twelve months of the year is seen in the following table[69]: _The Yearly Periods of Cyclone Frequency in Several Seas_ ------------+---------+---------+----------+----------+-------+------- | Arabian | Bay of | S. Indian| Java | China | | Sea. | Bengal. | Ocean. | Sea. | Sea. |Havana. ------------+---------+---------+----------+----------+-------+------- No. of years| 234 | 139 | 40 | -- | 85 | 363 No. of | | | | | | cyclones | 70 | 115 | 53 | 12 | 214 | 355 | | |Piddington|Piddington| Authority. |Chambers.|Blanford.|Thom and |and |Schuck.| Poey. | | |Reid. |Thom. | | ------------+---------+---------+----------+----------+-------+------- Jan | 6 | 2 | 17 | 25 | 2 | 1 Feb | 4 | 0 | 25 | 42 | 0 | 2 Mar | 3 | 2 | 19 | 8 | 2 | 3 April | 13 | 8 | 15 | 8 | 2 | 3 May | 18 | 16 | 7 | 0 | 5 | 1 June | 29 | 9 | 0 | 0 | 5 | 3 July | 3 | 3 | 0 | 0 | 10 | 12 Aug | 3 | 4 | 0 | 0 | 19 | 27 Sept | 4 | 5 | 2 | 0 | 27 | 23 Oct | 6 | 27 | 2 | 0 | 16 | 17 Nov | 14 | 16 | 7 | 0 | 8 | 5 Dec | 3 | 8 | 6 | 17 | 3 | 2 ------------+---------+---------+----------+----------+-------+-------