In Egypt several causes occurred, which in any country, separately applied, would be adequate to the production of violent ophthalmia. The dry, white, dazzling, soil, and the fine sand and dust constantly thrown about in whirlwinds and entering every crevice. If an ophthalmia is epidemical or is endemic in Egypt, the above causes will render it a very violent disease. But I conceive, that, of themselves and alone, these circumstances do not produce the violent ophthalmia seen in Egypt. In no place did these circumstances exist in greater force than at Kossier, on the march across the Great Desert, and at Ghenné. Yet, till our arrival at Ghiza, the disease did not appear. These circumstances likewise exist in great force in most places of India, where the ophthalmia occasionally occurs from them, yet it is different from the two first species of the Egyptian ophthalmia. For the production of the third species of this disease, the same causes will account, which produce dysentery, hepatitis, and other diseases of the liver. In Egypt, I remarked, that most of the cases of this species occurred at the time that dysentery prevailed the most. It should be mentioned, that, in Egypt, the natives are universally impressed with the idea, that sleeping in the night-air brings on the disease. In the ophthalmia of Egypt, as in the plague, it would appear, that very much may be done in the prevention. It could not escape observation, how rarely officers were the subjects of this disease. In accounting for this, I lay most stress on the attention which officers pay to cleanliness. In the 88th regiment, where, I believe, forty men did not escape an attack, only two officers out of thirty had ophthalmia. In the whole of the Indian army, only one officer lost an eye by it, and this was Ensign Paton, of the 86th regiment. The exemption of the officers from the ophthalmia gives more weight to the opinion, that in Egypt this disease is communicated by contagion. Mr Paton, previously to embracing the military profession, had studied medicine; and, when medical assistance was much wanted, and a great many of his corps were laid up with the ophthalmia, he very humanely offered to attend them. When employed in this duty, he was himself attacked with the disease and suffered most severely by it for many months. Mr Bellars, about this time, joined the 86th regiment at Ghiza; he took charge of the sick, and was attacked in the same manner as Mr Paton had been, and he likewise suffered most severely by it for several months.