"Very few, I imagine, of the original doubters remain unconverted,"Bays Dr. Watson, "to the doctrine which I have held from the beginning, that epidemic Cholera is catching: that it results from a material poison which is portable, capable of being conveyed from place to place, and communicated from person to person."

In his statistical report of the Royal Navy, published in 1858, Dr. Bryson says: "The medical records of the service have been searched in vain to discover an instance in which either Cholera Morbus or Yellow Fever made its appearance amongst a ship's company, unless one or more of the men or officers had previously-within at most twenty-one days-been exposed in some house, ship, or locality where the infectious virus which emanates from persons ill of the one or the other of these diseases existed. The spontaneous origin of either malady, far away from an infected locality, is unknown in the naval service.

"That the atmosphere forms one vehicle of infection seems clearly proved by some incidents ascertained respecting the last epidemic before it struck this country. I copy them from the ' Times' newspaper for October 15 or 16, 1865: Five miles from Gibraltar stands the little town of San Roque; and San Roque and Gibraltar were abruptly smitten with the plague, not only on the same day, but almost at the same moment. At Gibraltar it was a sudden access of the malady; at San Roque a first outbreak. At a small town near Toulon the plague fell upon the place in the night; and thirty cases occurred simultaneously between evening and morning. At Constantinople it was observed that, while the Cholera was raging, all the seagulls which used to flit over the waters of the Bosphorus deserted the place, nor did they reappear till the disease had departed and the atmosphere became pure once more.

"Compare this with an extract from the ' Dublin Morning Register,' respecting the first epidemic, that of 1832:

"' A Westport correspondent, upon whose veracity we place reliance, has communicated to us the following extraordinary fact: In the demesne of the Marquis of Sligo, near Westport House, there is one of the largest rookeries in the West of Ireland. On the first or second day of the appearance of Cholera in this place, I was astonished to observe that all the rooks had disappeared; and for three weeks, during which the disease raged violently, these noisy tenants of the trees completely deserted their lofty habitations. In the meantime, the revenue police found immense numbers of them lying dead upon the shore near Erris, about ten miles distant. Upon the decline of the malady within the last few days, several of the old birds have again appeared in the neighbourhood of the rookery; but some of them seem unable, from exhaustion, to reach their rests. The number of birds now in the rookery is not a sixth of what it was three months ago.'

"A striking proof that the air may be a vehicle of infection, that the poison may enter the lungs with the breath, is furnished by the fact that two pilots took the disease in consequence of having their open boat towed by a ten-fathom rope at a considerable distance astern of the steamship England, on board of which Cholera was raging. They were never on board the vessel. Both of them had Cholera, and one of them died of it. Both took the disease home, and transmitted it to their families, near Halifax, where the disease had been unknown for many years.

"But, although the infection thus proceeding from the bodies or the excretions of the sick, and entering by the lungs the bodies of the healthy, may strike and destroy individuals here and there, it seems very doubtful whether the disorder can become epidemic, except in certain conditions of the atmosphere.'

"It appears from the report of Mr. Glaisher on this subject, that ' The first three epidemics were attended with a particular state of atmosphere, characterized by a prevalent mist, (he is speaking of London and its immediate neighborhood), thin in high places, dense in low. During the height of the epidemic in all cases, the reading of the barometer was remarkably high, and the atmosphere thick.

"Dr. Farr stated that the rate of mortality from Cholera in London was high or otherwise, according to the height above the level of the Thames at which the patients resided. That is, the peculiar state of atmosphere which carried or excited the disease was more or less dense as you ascended from the level of the Thames. Otherwise the height of the land would scarcely make a difference, as Cholera has prevailed at Bogota (1849), 9000 feet above the level of the sea; at Emmench in Persia, 7000 feet; and more than once in the city of Mexico, at an elevation of 7990 feet.

"The material poison of Cholera will be likely to gravitate, as the marsh poison gravitates, with which it has many points of resemblance, to the lowest point of the atmosphere; where unwholesome exhalations from the soil and from the water are the most abundant, and where the dispersing and diluting influence of winds is least felt. Indeed the air may be completely stagnant, while on the neighbouring heights a brisk breeze is blowing. The lower regions of the atmosphere are the hotter also as well as the moister; and under the agency of a high temperature the organic impurity with which the air is charged runs more readily into decomposition."

It is now pretty well ascertained that the Cholera poison, like the poison of Typhoid Fever, may be propagated by the using of contaminated water. Dr. Snow collected facts which "warranted the presumption that a most fearful outbreak of Cholera in Soho was attributable to the water of a certain pump, contaminated from a neigbouring sewer. A remarkable fact was reported by the late Sir William Lawrence. Bethlem Hospital, and an asylum for children, called the House of Occupation, stand near together on an open space of ground between fourteen and sixteen acres in extent, lying in the parish of St. George, Southwark. Being dissatisfied with the filthy water then supplied by the Lambeth Company, the Governors some forty years ago sank Artesian wells on the premises, and the pure water thus procured is used exclusively in the two institutions, which between them number about seven hundred residents. There was not a single case of Cholera in the Hospital or in the House of Occupation in any of the first three epidemics; although the disease prevailed extensively in the parish, and in the streets in their immediate vicinity.