6 VEGETABLE SUBSTANCES. 



nearly keeps pace with that of ship-building; and 

 there is little doubt that, from the time of Alfred, who 

 first gave England a navy capable of contending with 

 her enemies upon the sea, to that of Nelson, (about 

 nine hundred years afterwards,) in whom nautical skill 

 appears to have been raised to the greatest possible 

 height, the oak was the principal and essential material 

 in ship-building. It is more than probable that the 

 inferiority of some of our more recently built ships, 

 and the ravages which the dry-rot is making among 

 them, have arisen from the substitution of foreign oak 

 for that of native growth. A writer in a recent number 

 of the Quarterly Review has ascribed this evil to the 

 substitution of a foreign species of oak, in our own 

 plantations, instead of continuing the true native tree. 

 In the same way, the real Scotch fir has been gradu- 

 ally superseded by a very inferior species, bearing the 

 same name; and the reason in each case appears to 

 have been, that the seed of the spurious kind is much 

 more plentiful, and grows more easily, than that of 

 the real species. We subjoin the passage to which 

 we have alluded: 



" We may here notice a fact long known to bota- 

 nists, but of which our planters and purveyors of 

 timber appear to have had no suspicion, that there 

 are two distinct species of oak in England, the Quer- 

 cus robur, and the Quercus sessiliflora; the former 

 of which affords a close-grained, firm, solid timber, 

 rarely subject to rot; the other more loose and sappy, 

 very liable to rot, and not half so durable. This dif- 

 ference was noticed so early as the time of Ray ; and 

 Martyn, in his Flora Rustica, and Sir James Smith, 

 in his Flora Britannica, have added their testimonies 

 to the fact. The second species is supposed to have 

 been introduced, some two or three ages ago, from 

 the continent, where the oaks are chiefly of this latter 

 species, especially in the German forests, the timber 



