248 G. T. HARRIS ON THE 



hundred and forty-four square miles of unclaimed more or less 

 trackless moorland, broken with the principal tors for which 

 Dartmoor is famed, and which rise to just above 2,000 feet in 

 the northern portion. The whole surface is rolling and hilly, 

 and the district dealt with here is practically an elevated plateau 

 of about 1,100 feet altitude, from which rise the numerous hills 

 and tors to a height totalling from 1,600 to 2,040 feet. The 

 entire district forms the principal catchment area of the Devon- 

 shire water supply, and is covered with innumerable bogs and 

 rivulets which feed the rivers Dart, Teign, Tavy, Taw and 

 Okement, all of which have their head- waters in the higher 

 portion around the desolate waste of Cranmere. The bogs vary 

 in size and depth, and range from one of about thirty by twenty 

 yards on the one hand to the dangerous and extensive areas 

 of Raybarrow Mire in the northern portion and Fox Tor Mire 

 in the southern. Generally speaking, the bogs are confined to 

 the elevated plateau from which the higher portions of Dart- 

 moor rise, or to the lower slopes of these eminences, while small 

 moor pools and deep peat gullies are to be found on the higher 

 portions. Vast deposits of peat resting on a granite floor char- 

 acterise the whole district, even to the highest points of the 

 moor, and as a consequence the streams and bogs after even 

 slight rain become flooded with peaty water. 



In collecting over this area it was divided into five districts 

 for convenience in working, and these five constitute the divisions 

 used in the census table of species accompanying this paper. 

 It is obvious that in a district with so many individual bogs as 

 Dartmoor possesses, it would be impracticable to enumerate 

 the species of each bog separately, hence I have adopted the 

 plan of grouping the bogs into districts formed as naturally 

 as possible. The following short descriptions of the grouping 

 may be useful for reference, the numerals being those of the 

 districts in the table of species. 



I. Metherall. — This is the name of a moorland farm on the 

 eastern fringe of the moor, standing near the South Teign river. 

 The bogs in the district are principally on the long slope of Water 

 Hill which rises to the south, and that portion of moorland 

 known as Chagford Common. Other bogs are situated on 



