TIMBER; FORESTRY 351 



above mentioned. It was introduced from Europe in 1869 

 by a scientist living at Medford, near Boston, Massachu- 

 setts, in the course of some experiments on silk-produc- 

 ing insects. It soon escaped into his garden, but could 

 easily have been exterminated if prompt measures had been 

 taken to secure every patch of eggs deposited on trees 

 in the vicinity. This was not done, and the insects propa- 

 gated themselves, until after twenty years they began to be 

 troublesome. In 1890 efforts to extirpate the moth were 

 begun on a large scale, but though from 1890 to 1897 more 

 than $865,000 were expended by the state in destroying the 

 moth, it still remained a serious enemy to the trees over a 

 region some two hundred- square miles in area. By the aid 

 of United States government funds the insect is now held in 

 check, but no one can say when it will be exterminated. 



(5) Sheep and cattle must not be pastured in woods in 

 which they can seriously injure the value of the timber 

 product. Cattle do not usually do much damage in 

 forests which consist mainly of mature trees. They de- 

 stroy some young broad-leaved trees by browsing, but do 

 not molest young conifers. Sheep injure young seedling 

 trees by browsing, and they do much more serious damage, 

 particularly on hillsides and mountains, by grazing the 

 grass too closely and cutting the turf to pieces with their 

 sharp hoofs, so that it is dried up by the sun and washed 

 away by heavy rains. In the Rocky Mountain region and 

 along the Pacific slope in this country and over great 

 tracts in southern Europe, valuable forest land has been 

 converted into worthless rock and gravel-covered treeless 

 slopes as a result of sheep-pasturing. 



422. Tree-Planting. — In those portions of the country 

 which are naturally forest-covered it is not usually worth 



