150 Mr David Don on a new arrangement 



the generally regular disposition of the layers of the globe from 

 the centre to the circumference, in the order of their specific 

 gravity. The refrigeration would tend to establish a relation 

 between the capacity of the solid crust and the volume of the 

 interior mass still in a fluid condition; and the upheavings or pro- 

 minences would be the consequence of a diminution of the capa- 

 city of the solid crust, in consequence]of the " retraif produced 

 by the gradual refrigeration of the masses in the interior, 

 (p. 665). These are the views which M. de Beaumont enter- 

 tains. 



AN ATTEMPT AT A NEW ARRANGEMENT OF THE ERICACE-E. 



By David Don, Esq,, Libr, L. S., 8fc. Communicated hy 

 the Author. 



Among the numerous families which compose the vegetable 

 kingdom, few surpass the EricacecB in the diversity of their 

 forms, beauty of their flowers, or in the extent of their geogra- 

 phical distribution, which verges upon the ultimate limits of ve- 

 getation in both hemispheres. The direction of mountain-chains, 

 and especially of particular strata, such, for example, as siliceous 

 and micaceous deposits, appears to exercise an equally important 

 influence on the distribution of this family with the circumstances 

 of latitude and elevation. Species of the groups of Andi'omedecB 

 and VaccimecB traverse the Andes from one extremity to the 

 other ; and in Asia they extend from the Frozen Ocean to with- 

 in the Tropics ; colonies of them being found in almost every 

 branch of the Indian Alps. The similarity of the vegetation of 

 North America and Central Asia is strikingly exemplified in the 

 groups of this family which are peculiar to both regions, such as 

 RJiodorecB, MonotropecB, PyrolecB^ VacciniecB, and the aberrant 

 Ei'icecB. Some species are common to both continents, such as 

 Pyrolapicta, Monotropa Mor'isoniana, Bryanthus Stelleri, Cas- 

 slope tetragona, and Andromeda poli/blia ; the two last forming 

 likewise part of the European Flora. Europe and Africa alone 

 contain the normal Ericece* well characterized by their persist- 



• I ought, perhaps, to except the Calluna vulgaris., samples of which were 

 contained in a collection of dried plants from Newfoundland, given to me by 

 Mr Connack, who assured me they had been collected in that country. 



