After what I have said of the latitude of Sennaar, it will scarcely be necessary to repeat that the heats are excessive. The thermometer rises in the shade to 119°, but as I have observed of the heats of Arabia, so now I do in respect to those of Sennaar. The degree of the thermometer does not convey any idea of the effect the sun has upon the sensations of the body or the colour of the skin. Nations of blacks live within lat. 13° and 14°, when 10° south of them, nearly under the Line, all the people are white, as we had an opportunity of seeing daily in the Galla, whom we have described. Sennaar, which is in lat. 13°, is hotter, by the thermometer, 50 degrees, when the sun is most distant from it, than Gondar is, though a degree farther south, when the sun is vertical. Cold and hot are terms merely relative, not determined by the latitude, but elevation of the place; when, therefore, we say hot, some other explanation is necessary concerning the place where we are, in order to give an adequate idea of the sensations of that heat upon the body, and the effects of it upon the lungs. The degree of the thermometer conveys this very imperfectly; 90° is excessively hot at Loheia in Arabia Felix, and yet the latitude of Loheia is but 15°, whereas 90° at Sennaar is, as to sense, only warm, although Sennaar, as we have said, is in lat. 13°. At Sennaar, then, I call it _cold_, when one, fully cloathed and at rest, feels himself in want of fire. I call it _cool_, when one, fully cloathed and at rest, feels he could bear more covering all over, or in part, more than he has then on. I call it _temperate_, when a man, so cloathed and at rest, feels no such want, and can take moderate exercise, such as walking about a room without sweating. I call it _warm_, when a man, so cloathed, does not sweat when at rest, but, upon moderate motion, sweats, and again cools. I call it _hot_, when a man sweats at rest, and excessively on moderate motion. I call it _very hot_, when a man, with thin or little cloathing, sweats much though at rest. I call it _excessive hot_, when a man, in his shirt, at rest, sweats excessively, when all motion is painful, and the knees feel feeble as if after a fever. I call it _extreme hot_, when the strength fails, a disposition to faint comes on, a straitness is found in the temples, as if a small cord was drawn tight around the head, the voice impaired, the skin dry, and the head seems more than ordinary large and light. This, I apprehend, denotes death at hand, as we have seen in the instance of Imhanzara, in our journey to Teawa; but this is rarely or never effected by the sun alone, without the addition of that poisonous wind which pursued us through Atbara, and will be more particularly described in our journey down the desert, to which Heaven, in pity to mankind, has confined it, and where it has, no doubt, contributed to the total extinction of every thing that hath the breath of life. A thermometer graduated upon this scale