4 INTRODUCTORY EXPLANATIONS. 



in Shetland than in Orkney. And under these circum- 

 stances, it appeared that at least the same mean of 46° 

 must still be indicated for species which occur at or near 

 the coast level in Shetland. 



But it has been since suggested by Mons. C. Martin, 

 and apparently with tnith, that the thermometrical registry 

 used by Mr. Edmondston in his tables, was taken fi-om an 

 instrument placed inside a room, although one without fire ; 

 and that it is consequently too high. (See Voyages en 

 Scandinavie, &c.) Mr. Martin prefers to substitute the 

 thermometrical observations made in the same island of 

 Unst, in 1824 and 1825, by Mr. WiUiam Scott, corrected 

 for time according to the scale deduced from observations 

 at Edinburgh, by Mr. Adie. He thus reduces the mean 

 annual temperature of Unst, situate at the northern extre- 

 mity of the Shetland group, to a fraction below 45° ; — say 

 45° for the gi'oup generally. 



The necessary correction will be made in the fonner 

 volume of the Cybele, by indicating that degree of tempe- 

 rature for any species which grows in Shetland, and is not 

 known to occur at such an elevation there, or elsewhere in 

 Britain, as would imply a mean temperatm'e below 45° 

 Fahr. The following species are thus circumstanced: — 

 Cakile maritima, Cochlearia officinalis, Cochlearia danica, 

 Sagina maritima, Arenaria marina, Cerastium semidecan- 

 drum, Cerastium nigrescens, Hypericum perforatum, La- 

 thyrus maritimus, Hippuris vulgaris, Eryngium maritimum, 

 Ligusticum scoticum, Daucus Carota, Anthriscus vulgaris ; 

 — for each of which the figure must be reduced from 46 

 to 45. 



