838 On the Incipi&nt Disengagement of Elastic Fluids. 



Considering how little we are acquainted with the Fauna of 

 that portion of Africa, which is situated between the equator 

 and the tropic of Capricorn, a closer examination of this small 

 collection cannot but furnish matter for very interesting obser- 

 vations.* A few species only have hitherto been published, 

 in particular by Messrs Olivier and Laporte (Hist. Nat. d. 

 Ins. Suit, a Buff., where Dongola seems sometimes to have, by 

 mistake, been substituted for Angola.) 



It is impossible to give a detailed account of the various re- 

 lations of the Fauna, until a collection has been subjected to a 

 thorough and minute investigation. Obscure species, as well 

 as those generally known and widely diffused, are in that case 

 of equal importance with those newly discovered or looked upon 

 as great rarities.t 



On the Incipient Disetigagement of Elastic Fluids. By John 

 Thomas Woodhouse, M.D., Senior Fellow of Caius Col- 

 lege, Cambridge. Communicated by the Author. 



I have never seen or heard a satisfactory explanation of the 

 well-known fact, that when a tea-kettle with boiling water in 

 it, is removed from the fire, the bottom is only moderately 

 warm. It has been referred to like causes (substituting steam 

 for vapour), as when spirits are thrown upon the skin, and a 

 sensation of cold is produced^ in which case heat is first given 

 to the fluid, succeeded by a change in the state of the fluid. 



This explanation appears to me defective and unsatisfactory ; 

 and I will now endeavour to shew where it is defective, and 

 supply the defect. 



When the kettle boils, the water in it will raise the thermo- 



* The few butterflies are not worth considering, because^ being chiefly 

 Species of Antocharis and Lyosena, they exhibit nothing characteristic 

 of the Fauna of Angola. 



t From Erichson's Archiv fur Naturgeschichtej 1843, part 3d, p. 199. 

 We hope, on a future occasion, to lay before our readers Professor 

 Erichson's particular details. — Edit. 



