.348 THE GROUSE IN HEALTH AND IN DISEASE 



sporting rents represent five, in cases ten times the value of the 

 grazing rents. 



The third period begins with the years of disaster 1872 

 and 1873, which were followed by four years of recovery and 

 very restricted bags. These lean years were the immediate 

 cause of the study of Grouse pathology. The investigation has 

 continued more or less ever since, and after passing through 

 the vicissitudes customary to research in a new field, has cul- 

 minated in the comparatively extensive knowledge of the 

 present day. 



Notwithstanding the fact that Cobbold had indicated in 

 1873 that the cause of the great outbreak was the Strongyle 

 worm, the first move towards an improved system of manage- 

 ment was not in the right direction. The moors had been 

 indifferently burned so long, that in order to catch up the rotation 

 recourse should have been had to big fires rather than to the patch 

 or strip system of burning. This, however, was not realised. 



Many land-owners, seeing that " patch-burned " moors were 

 less affected by the disease than moors on which no heather had 

 been burned, jumped to the conclusion that it was the smallness 

 of size of the individual patch, and not the total area of the burn- 

 ing that was all-important. This belief is prevalent in many 

 localities to-day, and it is no exaggeration to say that to this 

 error, more than to any other cause, is due the persistent 

 recurrence of disease. 



From the foregoing history of past failures, and the knowledge 

 scientific investigation has given us, we can proceed to lay down 

 with some approach to certainty the following rules of heather- 

 burning, and the reasons on which they are based : 



(1) That, in order to maintain the vitality and therefore 



the power of resistance of the Grouse, the moor must 

 be so burned as to keep the food-supply at its highest. 



(2) That the early spring food-supply is the index of the 



carrying capacity of a moor, and that therefore heather- 

 burning must be so ordered as to insure the maximum 

 yield of food in February, March, April, and May. 



