192 Scientific Intelligence. Meteorology. 



formed me, that upon the same night, there appeared to them 

 a light which greatly annoyed them. It appeared like a fur- 

 nace standing in the water, and the beams of the light stood 

 to a great height. It became fainter on the approach of day, 

 and at length vanished away by day-light. It continued for 

 two nights. It stood so near some of the boats that the men 

 thought of cutting from their lines to get out of its way." 



8. Tropical Nights. By the by, I travelled by night, to 

 avoid the heat of the mid-day vertical sun, and I now, from ex- 

 perience, advise my friends never to follow my example. No 

 evaporation takes place, you perspire copiously, with which, and 

 the excessive dew, your clothes get saturated, hanging on you 

 like wet leather, impeding every motion, and thus increasing 

 your fatigue. Your breathing is less free, and you get an oc- 

 casional puff of cold damp air, which, instead of refreshing, only 

 adds to your discomfort ; in short, you become completely op- 

 pressed. But in the sun, what a change ; evaporation rapidly 

 progresses, your dress acts like a wine-cooler, you get rid of the 

 oppressive sense of heat, become stimulated, and march on ex- 

 cessively relieved. One point, however, must never be neglected, 

 to keep a considerable thickness of clothing upon your head ; 

 you may then bid defiance to mere heat. On this subject of 

 tropical nights, it occurs to me that there is a rather singular 

 affection to which the human frame is subject ; and several me- 

 dical gentlemen, to whom I have spoken, seem to me to entertain 

 rather erroneous views as to its origin. I allude to what is vul- 

 garly called being moon-struck. Dr Wells, in his admirable 

 Essay on Dew, has shewn that a mutual interchange of radiated 

 heat takes place, in ordinary circumstances, between all bodies, 

 and that on this depends the preservation of temperature. On 

 brilliant moon-light and other cloudless nights, however, all ex- 

 posed bodies do not receive a quantity equal to that which they 

 shed forth. The want of clouds prevents them receiving that vast 

 quantity which would otherwise be shot back from the sky; in 

 consequence, equality of temperature is not maintained. AH 

 those bodies which lie favourably, some more than others, be- 

 come much cooled down, and, among other effects, moisture is 

 deposited from the little portion of air, cooled by contact, in the 

 immediate vicinity of the bodies. The human body, when ex- 



