Philosophical Transactions. 125 



ceros, the bear, and an animal of the deer kind, and of another 

 animal of the size of the bear. Mr. Whidbey abstains from any 

 speculations respecting the catastrophe by which these bones 

 were thus entombed in the solid rock, and properly enough rests 

 content with a naked statement of what he considers to be the 

 fact. 



The late volumes of the Philosophical Transactions have 

 abounded in important contributions to physical science, and 

 the part before us is, in this respect, not deficient ; it includes a 

 paper on the magnetic pheenoniena produced by electricity, by 

 Sir H. Davy ; two important communications, results of the 

 accurate diligence of Captain Kater ; and a notice from the same, 

 respecting a volcanic appearance in the moon ; and lastly, an 

 account of a micrometer made of rock crystal, by Mr. Dollond. 



Having thus generally surveyed the contents of this volume, 

 we shall proceed in a few instances to particularize their 

 details. 



i. On the black Rete Mucosum of the Negro, being a Defence 

 against the scorching Effects of the Sun's Rays, By SirE. 

 Home, Bart., F.R.S. 



As black surfaces become infinitely more heated than white, 

 by exposure to the sun's rays, it has long puzzled physiologists 

 to account for the black colour of the negro ; or to develope the 

 ends attained by that intensity of colour bestowed by the un- 

 erring hand of nature upon the inhabitants of tropical climates. 

 In this paper Sir Everard has rendered it probable that the 

 blistering and irritation which Europeans, not accustomed to 

 much exposure, suflFer from the scorching rays of an equatorial 

 sun, is attributable to a peculiar effect of the solar radiant matter, 

 unconnected with the heat which it excites. By the black 

 colour of the negro's skin the radiant matter of the sun is ab- 

 sorbed, and converted into sensible or thermometric heat, and 

 is thus disarmed of its mischievous tendency. 



If we expose the back of the hand to very intense sunshine, 

 uncovered, or covered with any thin white tissue, it becomes 

 inflamed and blistered ; but if similarly exposed under a cover- 

 ing of black, it suffers no inconvenience, though the temperature 

 in the former case falls far short of that excited in the latter. 



Having described a variety of experiments to this point, Sir 

 Everard very properly takes opportunity to observe that " the 

 same wise Providence which has given so extraordinary a pro- 

 vision to the negro for the defence of his skin while living within 

 the tropics, has extended it to the bottom of the eye, which 

 otherwise would suffer in a greater or less degree when exposed 



