fall into another error of diet, which contributes to the injury of their health: I mean, the employment of too large a proportion of heating animal food, which must often be in a state by no means the most wholesome.

Another error which Englishmen are apt to commit in warm climates, is the imprudent exposure of their persons at unseasonable hours of the day. Instead of adopting the course pursued by the natives, who may be supposed to be directed by experience, they too often omit to take shelter and repose during the hours of intense heat, in the middle of the day. Even in the South of Europe, where the heat scarcely admits of comparison with that within the tropics, the natives, during the middle of the day in summer, almost with one accord retire to bed. This mid-day desertion of the streets cannot fail to be very striking to our countrymen, who are unaccustomed to such a sight. Without being apprised of the cause, one would imagine that pestilence, or some other great and general calamity, had caused the town to be deserted. It is at this time, as the natives observe, that dogs and the English are the only living creatures to be found in the streets. In our own country, the most serious consequences, sometimes, though very rarely, follow continued exertion under the noon-day sun. Such accidents most frequently happen to those engaged in the harvests of hay and corn, who, from such undue exposure, sometimes experience an effect similar to that which is not unfrequent in hot climates, and is known by the name of the stroke of the sun'; which, when not quickly fatal, is mostly followed by alarming fever, or some most serious affection of the brain. The hint which these remarks are designed to convey might therefore with advantage be received and acted

upon by some classes in this country, as well as by those who visit warm climates. Renewed vigour, as well as protection from sickness, would well repay the labourer for retiring to some shady but dry spot during the hours of excessive heat, which is only felt during a small part of a few of our summer and autumnal days.

Another error not unfrequent on the part of our countrymen, when they visit some of the most unhealthful tropical climates, is the opposite to that which I have just mentioned; yet it is often rendered additionally injurious by being combined with it:I mean, exposure to the open air at nightfall, when dew renders the atmosphere peculiarly loaded with moisture, and when those unhealthful vapours, which seem to be the seeds of fever, are peculiarly intense and powerful. Our sailors are sometimes exposed to both these evils, in procuring water, and other stores, on the low shores of some tropical countries. The morning would, in all probability, be the most favourable time for the execution of such work; but when this time could not be devoted to it, I believe that even the middle of the night would be far better than the evening, especially if the body were protected with additional clothing, as well as not rendered unduly susceptible by the noon-day exposure, of which I have been just speaking. This last suggestion may also find some scope for application in this country, more particularly in the aguish districts of Kent, Essex, and Cambridgeshire.

Dismissing the subject of heat, I must now make a few remarks respecting the opposite state, or cold, as connected with some of the arts or callings of life. Although an extreme degree of cold is sufficient to

less than that of heat.

produce speedy death-of which the fact, that man and the inferior animals have sometimes been frozen to death, is a sufficient proof—it is very certain, that within the range of temperature to which most of us have access, the destructive influence of cold is very much This assertion may afford you some surprise, since in common conversation we hear a very large proportion of cases of indisposition attributed to cold. On careful inquiry, however, it will be often ascertained, that in these instances there has been no exposure to an intense degree of cold; but that the true cause of the injury received, is to be attributed to a partial application of a moderatelyreduced temperature; as when a draught of air comes through a hole or narrow crevice, upon an unprotected part of the body; the pernicious effect of which has long been well known, as we may conclude from its being the subject of a warning adage, to the following effect: "When the wind comes upon you through a hole, It is time to make your will, and take care of your soul." Such partial exposure, to a temperature which, in comparison with the warmth of the rest of the body, may be considered as cold, appears to be injurious, by giving rise to local inflammations. Sudden transition from one degree of temperature to another is likewise a cause of exposure to a very moderate degree of cold being regarded as productive of mischief to the health. But even in these cases it is not the perception of cold only which is to be taken into the account: the relaxing warmth to which the person has, in all probability, been accustomed, and by which the susceptibility to cold is increased and the power of resisting is diminished, must be taken into the account. The sudden return from cold to

warmth has also a very considerable share in producing those ill consequences which we are in the habit of setting down to the charge of cold alone. This observation is most strikingly illustrated in the case of parts which have been frost-bitten, in which state cold has nearly or quite put a stop to the processes of life going on in them. For a considerable time these processes are suspended, rather than abolished; and they may often be restored by a careful mode of treatment, in which the early application of warmth is forbidden, and which mainly consists of gentle friction with some material capable of keeping down returning warmth,-for which purpose, snow is not only the most easily obtained, but the best. An unguarded application of warmth would either lead to a distressing sore or chilblain, or occasion the death or gangrene of the part. Great practical advantage, with respect to the preservation of health, may be derived from a knowledge of the principles on which low or reduced temperature affects the living body. These principles are fully developed and illustrated in the very interesting work of Dr. Edwards, " On the Influence of Physical Agents on Life"; to which I have already had occasion to refer. Without attempting to notice all the conclusions to which he has arrived, I must mention one or two which bear particularly on the influence which the system receives from being kept for a considerable time at particular temperatures, and from the transition from such a temperature to one of an opposite character.

It has been clearly shewn by Dr. Edwards, that by a long continuance in a warm temperature, the power of producing animal heat, or, in other words, of resisting cold, is very much diminished. Thus animals produce less heat towards the close of summer

than they do after having lived through a winter's cold. We must all have been sensible, that the same temperature, as shewn by the thermometer, produces the effect of cold in autumn; but is oppressively warm in spring, when it is combined with the greater energy in the production of heat which we have acquired during exposure to the winter's cold. The degree of cold to which animal bodies are exposed, as well as the duration of the exposure, greatly influences the effect produced. The constitution of the individual exposed, is also a very important element in the result. When a person is plunged for a short time into a bath, which produces to his feelings the sensation of cold, he will generally experience, soon after coming out of it, a grateful glow of warmth; the stimulus to the production of heat continuing to operate after the application of cold has ceased. It is on this principle that the cold bath, suitably repeated, is of so much avail in invigorating the system. If the degree of cold be too great, and too long continued, the power of producing warmth, instead of being excited, is suppressed; and, instead of the glow which follows the proper use of the cold bath, there is a continued disagreeable sensation of cold, notwithstanding the individual may return to the same temperature, and put on the same dress to which he had been accustomed before his exposure to the cold. A striking instance of this kind occurred, in Paris, to a young man who fell into the river Seine, when it was frozen over. A considerable length of time elapsed before he could be rescued from the ice-cold water. This protracted and excessive cold so exhausted or oppressed his power of producing animal heat, that he could not get rid of the painful sensation for several days. The same