EXPANSION AND CONTRACTION OF SOLIDS BY HEAT. 3 



closed at the top, with a narrow entrance ; and builds in the neigh- 

 bourhood of a species of wasp, for the purpose, it is believed, of 

 rescuing it from the attacks of its enemies. The latter is of course 

 absurd, and the nest described by the prince must surely belong to 

 some other species. 



M. Salerne, as well as Vieillot, mentions its singular habit of sitting 

 crouched with its head drawn in betwixt the shoulders, so that the 

 hind head almost touches the back, giving it a very awkward appear- 

 ance ; and then it is so stupid as almost to permit itself to be taken by 

 hand. 



With respect to its voice, we have seen that M. Chervain says, " the 

 male has a feeble though pleasant warble ; " and M . Drapiez says it has 

 " a small song, rather agreeable, to which the female responds by a 

 small call-note." M. Vieillot says, " they make a frequent melancholy 

 noise." Ranzani says the female scolds (gridare) when the nest is 

 approached. 



" They are difficult to tame," says M. Montbeillard ; " yet we may 

 succeed if they are young, and fed by their parents in a cage till they 

 can feed themselves. They have a strong attachment to their brood, 

 and will not leave them as long as they hear them cry." This, how- 

 ever, is not peculiar to the green tody, but common to all birds. 



M. Temminck has made a genus of this single species; and 

 Baron Cuvier, M. Drapiez, and Signor Ranzani follow him. The 

 peculiar formation of the toes alluded to by R. H. L., is well known 

 to all systematic writers, and brings the bird under the division 

 Syndactyli. 



Editor. 



ON THE EXPANSION AND CONTRACTION OF SOLIDS 



BY HEAT. 



BY R. T. C. 



The principles of heat being associated with the pursuits of the 

 naturalist, the following, it is presumed, will not be misplaced by 

 occupying a space in the columns of the Field Naturalist. 



The particles of matter composing a solid body are kept at certain 

 distances from each other by two forces, viz. cohesion and repulsion. 

 If heat be applied to a solid, the attraction of cohesion is weakened, 



b 2 



