After the first edition of this part of the work was printed, an excellent institution was established at Portsmouth for the prevention of infection. A ship was appointed for the reception of the recruits of the fleet to which they were carried, to be stripped, washed, and provided with new apparel, before they joined their respective ships. This had a visible good effect on the health of the fleet; and it was planned and executed by Sir Charles Middleton, Comptroller of the Navy, whole unwearied assiduity, as well as integrity and ability in that important post, claim the highest praise and gratitude from his country. It follows farther, from the preceding observations, that there is a sort of risque in mixing two different sorts of men, even when there is no actual disease or suspicion of infection; for, whether it is from dormant infection, or merely from the circumstance of change of air, such mixtures are known from experience to be sometimes productive of sickness. The late Admiral Boscawen was so sensible of this, that he avoided it, unless when some evident utility or necessity of service made it proper; and upon this principle he used to resist the solicitation of captains when they requested to carry men from one ship to another upon changing their commands. One probable reason, among others, for ships of the line being more sickly than frigates or smaller ships is, that in greater numbers there is a greater chance of men of various descriptions and modes of life being mixed together. 2. Means of preventing the Production of Infection. The infection of fever is not always imported from without, but may be originally and spontaneously generated on board. The causes of this, as mentioned before, are want of personal cleanliness, and also confinement and crowding in close apartments.