The like delusion as to the _importation_ of disease is created by the appearance of fever amongst the migrants at sea. It is important that the universal effects of overcrowding, filth, and atmospheric impurity should be known and discriminated in all cases. It will be seen that they produce their effects at sea as well as elsewhere. It appears to be most important also to display the facts as to the common existence of the conditions of fever in ships themselves as at present regulated; and that, if properly regulated, instead of being fever-nests or “the means of importation” of the disease, a voyage in the open sea would become a sure means of arresting any such disease. Epidemic disease is often more severe in ships when stationary in port than when sailing, and with them the passage in fair weather when overcrowding is avoided is a means of mitigation. The sanitary regulation of the ships themselves—a measure of the utmost importance to the seafaring classes of the community—would accomplish far more than could be hoped for or pretended to be accomplished by any known system of quarantine, and would have, moreover, a beneficial effect upon popular opinion by removing the fallacious appearances which favour the belief in imported disease, while they divert attention from the true causes of disease, the removable and preventible causes that exist on the spot. The basis of sanitary legislation is the evidence that has been accumulated in relation to the whole of the epidemic, endemic, and contagious diseases, and the latest opinions of medical authorities with reference to them. It having been shown by indubitable evidence that the prevalence and mortality of typhus, scarlatina, cholera, and every other epidemic disease, are uniformly in proportion to the low sanitary condition of the population, the Legislature has decided on attempting to check the prevalence of these diseases by laying the foundation of sanitary improvement.[29] It appears that the measures adopted by the Legislature with this view should be consistently carried out and applied to the dwellings of all classes of the population whether on land or at sea. In the larger vessels in which well-directed care has been exercised, the general ill-health has been reduced below the average ill-health of populations of the like ages on shore; but from the evidence which has been brought from witnesses at the ports, medical men well acquainted from long practice in the mercantile marine, it appears that the _general_ condition of merchant-vessels, and of the forecastle in which common seamen are, for the most part, lodged, renders them in effect cellar-dwellings, just as dark, foul, and unventilated, as the filthy, unaired, and dismal cellars on shore with which the Legislature has endeavoured to deal. It appears also that typhus and other epidemic diseases do break out at sea in these movable cellars, just as they do in the cellars of the dirtiest courts on shore;