2. The life in the open air and the great amount of sunshine to be enjoyed; it is quite possible, under favorable circumstances, to pass fifteen hours daily in the open air; and whenever it is possible the traveler by sea is certain to endeavor to escape from the close and sometimes unpleasant atmosphere of a small cabin, into the pure air to be found on deck. 3. The great purity of the air at sea, and its entire freedom from organic dust and other impurities. In this respect it has an advantage over the air of an open country, for the latter is apt to contain the pollen of grasses and other plants, which, in some persons, excites hay fever and asthma. The air of the cabins may, of course, be contaminated, but the air of the open sea is probably the purest to be found anywhere. 4. The presence in the sea air of a large amount of ozone, as well as particles of saline matter, more particularly in stormy weather, from the sea spray, and these may exercise a beneficial effect in certain throat and pulmonary affections on the respiratory mucous membrane. 5. The great equability of the temperature at sea. This refers chiefly to the daily variations, which rarely exceed four or five degrees Fahr. It must be noted that in a long sea voyage very considerable variations of temperature are encountered, and in a swift steamer the transitions are somewhat sudden. 6. The great humidity of the atmosphere and the high barometric pressure, which are considered to exercise a useful sedative influence on certain constitutions. It is said that the temperature of the body averages one degree Fahr. less on account of this sedative effect. The exhilarating and tonic effect of rapid motion through the air; for by the continuous progress of the ship the sea breezes are constantly blowing over it, and the passengers are borne through the rapidly-moving air without any exertion of their own. The influence of these currents of air on the surface of the body is, no doubt, important, acting as a stimulant and a tonic, increasing evaporation from the skin, and imparting tone to the superficial blood-vessels.