102 NOVUM ORGANUM. 



tion ; 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 TenerifFe, walk by night and not in the day 

 time, and are advised and pressed by their guides, as soon 

 as the sun rises, to make haste in their descent, on account 

 of the danger (apparently arising from the rarity of the at 

 mosphere) lest their breathing should be relaxed and suffo 

 cated. 



Third negative to the second affirmative. 



The reflection of the solar rays in the polar regions is 

 found to be weak and inefficient in producing heat ; so that 

 the Dutch, who wintered in Nova Zembla, and expected that 

 their vessel would be freed about the beginning of July from 

 the obstruction of the mass of ice which had blocked it up, 

 were disappointed and obliged to embark in their boat. 

 Hence the direct rays of the sun appear to have but little 

 power even on the plain, and when reflected, unless they are 

 multiplied and condensed, which takes place when the sun 

 tends more to the perpendicular ; for then the incidence 

 of the rays occurs at more acute angles, so that the re 

 flected rays are nearer to each other, whilst, on the contrary, 

 when the sun is in a very oblique position, the angles of 

 incidence are very obtuse and the reflected rays at a greater 

 distance. In the mean time it must be observed, that there 

 may be many operations of the solar rays, relating too to 

 the nature of heat, which are not proportioned to our touch, 

 so that, with regard to us, they do not tend to produce 

 warmth, but, with regard to some other bodies, have their 

 due effect in producing it. 



Fourth negative to the second affirmative. 



Let the following experiment be made. Take a lens the 

 reverse of a burning glass, and place it between the hand 

 and the solar rays, and observe whether it diminish the 

 heat of the sun, as a burning glass increases it. For it is 

 clear, with regard to the visual rays, that, in proportion as 

 the lens is made of unequal thickness in the middle and at 

 its sides, the images appear either more diffused or con 

 tracted. It should be seen, therefore, if the same be true 

 with regard to heat. 



Fifth negative to the second affirmative. 



Let the experiment be well tried, whether the lunar rays 



