Vlll PREFACE. 



erred in the application of this kind of crossing to 

 practice in particular cases, but several entire breeds 

 have been lost which ought to have been preserved. 

 There are many breeds, indeed, so defective in them- 

 selves, that time and capital would have been lost in 

 endeavouring to cultivate them ; but not a few, as will 

 be seen in the sequel, might have been improved to 

 the degree required, by mere selection of parents, and 

 attention to the known principles of breeding. 



Not only do animals become adapted in constitution, 

 temperament, and habits, to the situations in which 

 they have been naturalized, but characters Communi- 

 cated by art become permanent by continued repro- 

 duction. Thus, in the case of the Dairy Breed of 

 Ayrshire, by breeding from females that possess the 

 property of yielding a large quantity of milk, a pecu- 

 liar breed has been at length formed, exceedingly well 

 suited to the purposes of the dairy, and at the same 

 time hardy and fitted to subsist on ordinary food. 

 Now, such a breed might be injured, and not im- 

 proved, by crossing even with a race superior to itself 

 in many properties. Thus, a cross with the Durham 

 or Hereford Breeds would produce animals of larger 

 size and superior fattening properties to the native 

 race ; but even in these properties, the progeny would 

 be inferior to either the Herefords or the Durhams, 

 and inferior, as a hardy race of dairy cattle, to the 

 Ayrshire Breed itself. Hence, the crossing of a breed 

 of cattle with a race apparently superior, will not 



