THE AGE OF TREES. 85 



been minuted in indelible writing the locality of the tree, the kind 

 of timber, the year and month when cut, the soil where it grew, 

 the side and point which faced the north, and every other circum- 

 stance which can possibly be supposed ever to have the remotest 

 relation to the value of the table in hand. The lover of science 

 will not be backward to incur such trouble, for be knows how 

 often in the progress of human knowledge an observation or an 

 experiment has lost its value by the disregard of some circum- 

 stance connected with it, which at the time was not thought 

 worthy of notice. Lastly, there might be attached to the same 

 section a written meteorological table compiled from the observa- 

 tions of some scientific person, if such observations had been made 

 in the vicinity. This being done, why, in this age of science, might 

 not this natural, unerring, graphical record of seasons past deserve 

 as careful preservation as a curious mineral, or a new form of 

 crystals ? " 



To ascertain the respective ages attained by different kinds of 

 ti-ees is not merely a curious inquiry which may pleasantly occupy 

 the time of an enlightened observer of nature, but it is one which 

 may reasonably be expected to produce useful results, determin- 

 ing points in the history of the globe, and throwing light on 

 many parts of vegetable physiology and the art of forestry. But 

 in order to make observations on this subject that shall be really 

 useful to the cause of science, we must first become acquainted 

 with a few simple laws by which the growth of trees is regulated. 

 Trees belong to two great classes, with the structure of which it 

 is necessary that we be acquainted. The first contains a much 

 larger number than the second, and presents more important 

 objects for consideration. The vegetables in it have a woody stem 

 and bark, and their method of growth is to add every year a new 

 woody layer on the outside of preceding ones, and immediately 

 within the bark. The new layers are therefore the most outward, 

 and the division is on this account named " exogenous," which 

 signifies increasing by addition to the outside. 



The second division is composed of vegetables, whose trunks, 

 cylindrical and seldom branching, present a woody stem, properly 

 speaking, without bark, whose outer fibres are older and harder, 

 while the inner are younger and softer. As the newest and latest 

 formed portions of these vegetables are within, the division is 

 termed " endogenous" which signifies increasing by addition to 

 the centre. 



