While on the subject of the causes or sources of disease, I may mention two which do not appear to me to have been sufficiently considered and provided against in India.  First, when a new cantonment is formed and occupied in haste, during or after a campaign, terraces are formed of the new earth dug up on the spot to elevate the dwellings of officers and soldiers from the ground, which may possibly become flooded in the rains; and over the piles of fresh earth officers commonly form wooden floors for their rooms to secure them from the damp, new earth.  Between this earth and the wooden floor a small space of a foot or two is commonly left.  The new earth, thus thrown up from places that may not have been dug or ploughed for ages, absorbs rapidly the oxygen from the air above, and gives out carbonic acid, nitrogen and hydrogen gases, which render the air above unfit for men to breathe.  This noxious air accumulates in the space below the wooden floor, and, passing through the crevices, is breathed by the officers and soldiers as they sleep.

Between the two campaigns against Nepal in 1814 and 1815, the brigade in which my regiment served formed such a cantonment at Nathpoor, on the right bank of the river Coosee.  The land which these cantonments occupied had been covered with a fine sward on which cattle grazed for ages, and was exceedingly rich in decayed vegetable and animal matter.  The place had been long remarked for its salubrity by the indigo-planters and merchants of all kinds who resided there; and on the ground which my regiment occupied there was a fine pucka-house, which the officer commanding the brigade and some of his staff occupied.  In the rains the whole plain, being very flat, was often covered with water, and thousands of cattle grazed upon it during the cold and hot seasons.  The officers all built small bungalows for themselves on the plan above described; and the medical officers all thought that they had, in doing so, taken all possible precautions.  The men were provided with huts, as much as possible on the same plan.  These dwellings were all ready before the rains set in, and officers and soldiers were in the finest state of health and spirits.

In the middle and latter part of the rains, officers and men began to suffer from a violent fever, which soon rendered the European officers and soldiers delirious, and prostrated the native officers and sipahees; so that three hundred of my own regiment, consisting of about seven hundred, were obliged to be sent to their homes on sick leave.  The greater number of those who remained continued to suffer, and a great many died.  Of about ten European officers present with my regiment, seven had the fever, and five died of it, almost all in a state of delirium.  I was myself one of the two who survived, and I was for many days delirious.