hygrometric state of the atmosphere, we are enabled to calculate, pretty accurately, the quantum of injury the men will be exposed to in washing decks, and to ascertain the fittest weather to be chosen for that purpose..

The best hygrometric measure is that recommended by Mr. Colebrooke. Two thermometers, with the scales detached from the bulb, are to be used. The bulb of the one is to be wetted with a rag, and, after a short time, the mercury will be observed to fall to that point at which condensation of vapour takes place. And the difference between this point, and the other thermometer, shewing the temperature of the atmosphere, will give the exact degree of dryness in the air; or, in other words, its capacity for moisture.

When (as already stated) the air has a great capacity for moisture, much injury will be sustained by those exposed to it, and vice versa.

diminish the temperature of the body, unless the temperature of it be below 629; if it is above that, it increases it." -Cullen's First Lines, vol. I. p. 130.

Although this observation may be generally correct, yet there are circumstances where I most humbly beg to differ from this celebrated physician. An individual, living in a moist lower deck, for instance, at a time when the air has a great capacity for moisture, will experience the sensation of cold, though the thermometer may range several degrees above 62°; besides, the cooling process is much increased by diminished atmospheric pressure.

Of Sick-Lists.

EVERY surgeon in the royal navy ought to keep two sick-lists; (some now do,) the first, containing those men's names who are totally incapable of performing any kind of duty, called the Sicklist; and, in the second, or Convalescing-list, those men's names are to be entered, who are in a state of progressive improvement from disease to full health; those also who have recently been, under the influence of mercury, and those who have a disposition to pulmonary and hepatic affections, (although they may be free from complaint at the time,) are to be considered on this list, at least, during washing of decks.

All convalescing patients should only receive, half allowance of grog, and this ought to be considered the sine qua non of that list, as it will have a beneficial tendency two ways; first, inas much as it will be sufficient for the patient's present state of health, and secondly, the high regard he generally has for it as a whole, will prevent him hanging on the surgeon's hands.

By following the above regulations, we should have a large convalescing-list, it is true; but then the sick-list would be proportionately kept down, as well as so frequent recurrence of acute disease.

OF

DRY ROT IN SHIPS.

"Water restrain'd gives birth

"To grass and plants, and thickens into earth."

PRIOR.

屬

THE following observations on Dry Rot in Ships, will be considered, by many, as going out of my department; but, perhaps, I may be excused, when it is recollected, that a Man of War in a rapid consumption, is not only a melancholy spectacle in itself, but is rendered doubly so, in associating this national loss with a conviction that a ship's crew cannot remain long in a healthy state, when the martial walls of their habitation are quickly mouldering into dust. Moreover, the study of the laws which regulate heat and cold, moisture and aridity, (the chief agents of destruction) are closely linked with the duties of a professional man, and the growth and dissolution of all organized bodies, ought to be

familiar to him. Besides, the means hereafter to be pointed out for the peservation of His Majesty's ships, will also have a salutary tendency on the health of our seamen, and, on that account, have a double claim to our attention.sds Notwithstanding that apparently endless va riety which we observe in the vegetable king dom, it appears, on analysis, that Nature has employed only three simple substances, oxygen, hydrogen, and carbon, in the formation of all the gradations of vegetable productions, from the majestic oak, to the dunghill mushroom.*

And, what is equally wonderful, the natural food of the fifty thousand plants already known, is as simple and uniform as their component parts: they all require atmospheric air and water only, with the addition of light and caloric to produce vegetation.+

Some plants are said to yield, also, small traces of nitrogen, silex, and lime, &c. but these substances have undoubtedly been taken up by the roots.

↑ When we attempt to follow Nature farther, and consider the endless variety there must be in the vessels and secreting organs of plants, in order to endow them with the power of producing that countless number of fruits, oils, resins, wax, sugar, &c. which we observe in Nature; and when we remember, that trees of every description, from the cedar to the shrub, and plants, from those of the most sensensitive kind within the Tropics, to the most hardy ever

Mr. Parkes observes, that all living vegetables have the power of decomposing water, and combining, in different proportions, the hydrogen of the water with the carbon of the soil, as well as that of the carbonic acid of the atmosphere, to form the numberless productions of vegetable nature. 456

con

It is delightful to trace the chain of nexion between life and death in vegetables, and contemplate on the important offices which water has to perform, during the growth and dissolution of the vegetable kingdom.

Death is the common consequence of all life, and, during that continual decomposition of one generation of plants after another, which takes place in every part of the terrestrial globe, a great quantity of carbonic acid is liberated in union with hydrogen, by which our atmosphere would soon have become contaminated, had not some means been provided for its renovation.

green in our own regions-and herbs, of every shade of colour and quality, the most delicious, as well as those of the most poisonous nature, are all formed from the same simple substances, (though combined in different proportions;) we arrive at the ne plus ultra of human understanding, and are compelled to stop and wonder that such different products should be heated by one sun, fed by the same common nutriment, and grow in the same medium.