76 baker's north YORKSHIRE. 



The Infer-agrarian zone includes the lower levels of the surface 

 in the country south of the estuaries of the Dee and the 

 Humber, the Mid-agrarian zone the lower levels of the district 

 which extends from these as far north as the estuaries of the Tay 

 and the Clyde, and the Super-agrarian zone the lower levels of 

 that portion of Scotland which is still unaccounted for. Above 

 the limit of cultivation the ' three zones of the Arctic Region 

 may be traced in ascending the loftier mountains of the north, a 

 convenient line of demarcation being furnished by the upper 

 limit of Erica Tetralix to bound the lowest of the three in an 

 upward direction, and of Calluna vulgaris to separate the two 

 others. Numbering these zones from one to six, beginning with 

 the warmest, we may conveniently and at the same time com- 

 prehensively indicate the range of temperature which we possess 

 within the limits of our field of study, as compared with that of 

 Britain as a whole, by saying that we have in North Yorkshire 

 three out of these six zones, the second, the third and the fourth, 

 that the lowest levels of the surface are not warm enough to 

 attain the comparatively southern temperature of the Infer- 

 agrarian zone, nor its highest summits elevated enough to reach 

 the comparatively colder temperatures of the two upper zones of 

 the Arctic Region. These three zones then, we will adopt, and 

 as there is no need to use long words where short ones will 

 answer the purpose equally well, we shall speak of them through- 

 out these notes simply as the Upper, the Middle and the Lower 

 zone, the Upper being the Infer-arctic, the Middle the Super- 

 agrarian, and the Lower the Mid-agrarian of the ' Cybele.' 



Mean Temperatures in the Shade. — For York we have two 

 thoroughly reliable sets of observations, in both cases made with 

 instruments manufactured and corrected for special researches. 

 The observations of the late Jonathan Gray extended from 1801 

 to 1825, three observations being taken daily and the results 

 reduced to mean values by the proper tables. The observations 

 of my valued friend John Ford at York have now extended over 

 upwards of twenty years and are still (1863) continued. These 



