8OOR II.] APHORISMS. 469 



Proximate Instances wanting the Nature oj Heat. 



The rays of the moon, stars, and comets, arc not found to bo 

 warm to the touch, nay, the severest cold lias been observed to 

 take place at the full of the moon. Yet the larger fixed stars are 

 supposed to increase and render more intense the heat of the 

 sun, as he approaches them, when the sun is in the sign of the 

 lion for instance, and in the dog-days. 



The rays of the sun in what is called the middle region of the 

 air give no heat, to account for which the commonly assigned 

 reason is satisfactory; namely, that that region is neither suffi 

 ciently near to the body of the sun -whence the rays emanate, 

 nor to the earth whence they are reflected. And the fact is 

 manifested by snow being perpetual on the tops of mountains, 

 unless extremely lofty. But it is observed on the other hand by 

 some, that at the Peak of TenerifFe, and also among the Andes ot 

 Peru, the tops of the mountains are free from snow, which only 

 lies in the lowej* part as you ascend. Besides, the air on the 

 summit of these mountains is found to be by no means cold, but 

 only thin and sharp ; so much so, that in the Andes it pricks and 

 hurts the eyes from its extreme sharpness, and even excites the 

 orifice of the stomach and produces vomiting. The ancients 

 also observed, that the rarity of the air on the summit of Olympus 

 was such, that those who ascended it were obliged to carry sponges 

 moistened with vinegar and water, and to apply them now and 

 then to their nostrils, as the air was not dense enough for their 

 respiration; on the summit of which mountain it is also related, 

 there reigned so great a serenity and calm, free from rain, snow, 

 or wind, that the letters traced upon the ashes of the sacrifices 

 on the altar of Jupiter, by the fingers of those who had offered 

 them, would remain undisturbed till the next year. Those even, 

 who at this day go to the top of the Peak of TcncriiFe, walk by 

 night and not in the day-time, and arc advised and pressed by 

 their guides, as soon as the sun rises, to make haste in their 

 descent, on account of the clanger (apparently arising from the 

 rarity of the atmosphere), lest their breathing should be relaxed 

 and suffocated. p 



This notion, which he repeats again, and particularizes in the 

 ISth aph. of this book, is borrowed from the ancients, and we need not 

 Bay is as wise as their other astronomical conjectures. The sun also 

 approaches stars quite as large in other quarters of the zodiac, when it 

 looks down upon the earth through the murky clouds of winter. \Vhen 

 that luminary is in Leo, the heat of the earth is certainly greater than 

 at any other period, but this arises from the accumulation ot heat after 

 the solstice, for the same reason that the maximum heat oi the day is at 

 two o clock instead of noon. Ed. 



P Bouguer, employed by Louis XIV. in philoBophical rese \rclioe, 



