Sulphur dioxide and sulphuretted hydrogen are present in volcanic exhalations and in many mineral waters.
The dioxide has been known since the earliest times and is found as a naturally occurring product in the gaseous exhalations of volcanoes and in solution in some volcanic springs.
The miasmatic exhalations caused by the sun playing on stagnant waters after the floods give rise to the "Sennar fever," which drives even the natives from the plains to the southern uplands.
Owing to the noxious exhalations of the surrounding forests the town is so extremely unhealthy during the hot weather as to have acquired the title of the "Abode of the Plague."
There are neither sulphuric exhalations nor escapes of steam at present, and it would seem that this great volcano is permanently extinct.
