CHAP, vi.] Advantages of Mixed Woods 127 



Dean, which were planted up for the purpose of supplying Oak 

 timber for the use of our navy. But now all our ships of war, 

 and the best classes of liners, are constructed almost entirely 

 of iron or steel and of Teak timber from Burma. Teak in 

 place of corroding iron with which it comes in contact, as Oak 

 does owing to its tannic acid is, through an essential oil 

 contained in it, preservative of the steel screws, bolts, &c. 

 But notwithstanding the present extensive and ever-increasing 

 use of substitutes like iron in place of timber, and the vast 

 improvements in communication by means of which the 

 forest produce of far-distant countries can be brought to 

 build the navies of Europe, and even to pave the streets of 

 London timber is, along with gold, almost the only com- 

 modity which has not during the past half century depreciated 

 in relative exchangeable value with most other articles of com- 

 merce. All classes of timber do not, however, command equally 

 favourable market quotations. But the sagacious sylviculturist 

 will easily know from a study of selling prices, of the stocks 

 of timber held at the chief marts, and of the reports as to 

 the probable quantity and the quality of imports from abroad, 

 what kinds and classes of timber are most likely to be re- 

 munerative in the immediate future. And it is self-apparent 

 that he will be in a far better position to tend and foster 

 those species which hold out the fairest financial promise, 

 when several kinds of trees are growing together in mixed 

 woods, than when each species forms a pure forest worked 

 quite independently of the other crops. 



Mention has above been made of the Oak woods planted by 

 the Crown for the future supply of navy timber, which is not 

 now required. As crooks were formerly an essential before 

 the framework of hulls was made of iron or steel, the most 

 economical method of producing them was to grow the Oaks 

 as standards enjoying as full supplies of light and air as possible. 

 But, under ordinary circumstances, the most economical manner 

 of growing Oak timber for general technical purposes (requiring 



