Sometimes it is the cargo itself which is a fatal cause of disease or death. Ships carrying large quantities of minerals, sulphur, petroleum, &c., sometimes smell intolerably, but are not considered unhealthy places of residence. But how of guano and other manure ships? In one of Dr. Stone’s letters to the _Times_, published in 1867, he says:—“The most objectionable and unhealthy cargoes brought into the Thames are those consisting of the different kinds of manure. A large bone trade is carried on in the port of London; barges are constantly passing up and down the Pool laden with bones collected from bone-dealers and the slaughter-houses of London. Many of the bones are not dry, but are covered with decomposing flesh. The smell is very bad, and is not limited to the immediate neighbourhood of the barge itself, but may be carried for a long distance. These bone barges discharge their cargoes into some small coasting ship.... The sailors and bargemen engaged in work of this kind suffer very much: they are nauseated by the offensive smell; their appetites fail entirely; they consume large quantities of spirit; and, as a consequence, are invariably attacked by diarrhœa, accompanied with vomiting. In the summer time it is a matter of surprise how anyone can remain, for a short time even, in the neighbourhood of the vessel; a thick offensive steam is constantly rising from the bones, and the decks and rigging are covered with large blue flies. When the vessel (generally a small, very old, and ill-manned schooner) puts to sea, the hatchways are kept open, so as to give free egress to the gaseous products of decomposition and to prevent the ship from taking fire.” Many have been the instances of ships’ decks being blown up by the gas from coal becoming ignited, and loss of life has been caused thereby. Gunpowder may, under certain conditions, become a most dangerous cargo. Take the case of the _Great Queensland_, which was blown up entirely, leaving no survivors to tell the tale. The cause is not far to seek when we learn that two tons of impure wood powder, sufficient of itself to burst the ship to pieces, and from its condition likely to explode, were stored in the same compartment with thirty tons of ordinary black gunpowder.