IV. PHYSICAL GEOGRAPHY. 130 



lute heiglit of the loftiest hills, those of one division com- 

 pared with those of the other. 



The local botany of West Britain is less fully ascer- 

 tained than that of East Britain ; the lists of si^ecies for 

 several of the western counties being still very incom- 

 pletely made out. Eegarded as a whole, the Western 

 flora is nearly as well ascertained as the Eastern flora ; 

 though some few segregate species, hitherto recorded 

 only on the eastern side of the island, may eventually be 

 found also on the western side. The letters " w. e." in 

 the Summary of Distribution, V, give a separated flora 

 for each side of the island. The substitution of blanks 

 " -," instead of letters, will indicate the species whose 

 presence in the one, and absence in the other, render the 

 floras of the western and eastern divisions non-identical. 



7. Vice-Counties. — The lines traced across the divided 

 counties on the Map, in volume third, will scarcely suffice 

 for botanists who may wish to distinguish these subordi- 

 nate sections on other maps. To facilitate recognition 

 the course of the dividing Unes shall be given here by 

 verbal explanation, adapted to the maps of England and 

 Scotland, published under the auspices of the ' Society 

 for the Diff"usion of Useful Knowledge.' In thus subdi- 

 viding the counties, any natural peculiarities were taken, 

 or even well-marked lines traceable on maps, and findable 

 on the actual ground ; such as water- sheds, roads, canals, 

 rivers, &c. — East and West Cornwall are separated by a 

 line traced along the high road from Truro, through St. 

 Columb, to the inland extremity of Padstow Creek. At 

 the two ends of this line, the salt-w^ater completes the di- 

 vision. — South and North Devon are separated by an ima- 

 ginary line, adapted to the water-shed ; commencing at the 

 Tamar, about midway between Tavistock and Launccston ; 



