Medical Topography of Upper Scinde. 219 



generated in low typhoid fevers, causes them to be infectious. 

 It is the immediate cause of death in very many cases of 

 conjestive typhoid fever which terminate in colliquative fluxes 

 in our Indian jails, by its influence as a direct sedative poison 

 on the brain and nervous system ; the manner of death being 

 exactly that which sulphuretted hydrogen, when breathed 

 from without, would occasion." These views are laid down 

 without the slightest hesitation ; and without the slightest 

 intimation that they are merely theoretical assumptions : but 

 he surely cannot expect his readers at Once to adopt them : 

 no one will deny that hydro-sulphuric acid is often deleteri- 

 ous to health, and Dr. Kirk may have had satisfactory reasons 

 for thinking it the cause of fever ; but if so, he keeps them 

 to himself: he does not make even an attempt to establish 

 their truth. 



With such views and prepossessions he proceeded to 

 Scinde, where he was called on to report on the causes of 

 the unhealthiness of Sukkur — and we cannot be surprised 

 to learn that he found no difficulty in finding that his favour- 

 ite agent was at work there also, however little this might 

 be obvious to common penetration. But before proceeding 

 further we must remark, that his views seem to have been 

 modified since 1844; as in the commencement of his present 

 memoir he recognises the existence of malaria " as a poisonous 

 emanation from marsh or moist lands," without assuming 

 that it is necessarily hydro-sulphuric acid. 



Our author soon satisfied himself, that the higher places 

 in Sukkur were unhealthy, while the plains were compara- 

 tively the reverse: as he found it to be highly improbable 

 that ordinary malaria should affect the hills, it immediately 

 struck him that their unhealthiness must be caused by some 

 peculiarity in their geological formation. According to his 

 account they are cretaceous rocks, somewhat like the chalk 

 of Britain, underneath which unspent volcanic action and 

 consequent generation of hydro-sulphuric acid are assumed 



