July 1, 1895.] 



KNOWLEDGE. 



163 



Kauschinger in his Lehre rom ^]'ahhcliut:, following 

 Hellman, calculates that if the liability of beech to be 

 struck by lightning be assumed at 1, that for conifers is 

 15, oak 54, and for other broad-leaved species 40. 

 Notwithstanding the isolated positions of thousands of oaks 

 all over the country and in mixed forests, with their towering 

 tops so " attractive " in a storm, no indigenous British tree 



'<■?- 





Li*i, 



j^ 



has withstood the attacks of so many terrific hurricanes 

 and lightning-strokes as bravely as the oak. There are 

 no humanly devised protective means against lightning in 

 forests, and, for practical sylvi-cultural purposes, none are 

 needed. Forest fires are extremely rarely, if ever, caused 

 by lightning, and if a large tree is struck and severely 

 damaged, no great loss is involved in clearing it away. 



The theory that the geological as well as the topo- 

 graphical conditions of certain localities " may have some 

 influence upon the frequency of lightning stroke " was 

 some time ago advanced by the meteorologist of the Koyal 

 Prussian Bureau of Statistics, to the effect that if 1 



represents the frequency of lightning stroke in a chalk 

 formation, 2 will represent the liability of marl, 7 for clay, 

 ;* for sand, and 22 for loam. Amongst other popular 

 fallacies, the following are successfully combated, namely ; 

 " That lightning never strikes the same place twice ; that 

 the most exposed position is always struck ; that a few 

 inches of glass or a few feet of air will serve as a competent 

 insulator to bar the progress of a flash that has forced its 

 way through a thousand feet of air." 



From time to time, paragraphs get into press circulation 

 (invariably reclidiifi's of ancient and well-worn legends) 

 from the hands of one or other of our " most eminent 

 popular scientists," about the fabulous ages of certain trees, 

 particularly oaks. The fact is, that we have no means of 

 knowing the exact, or even approximate, ages of trees of 

 very old growth, except by inductively reasoning from the 

 phenomena of tree ijroirt.Ji in relation to time, and tree 

 decti;/. The counting of rings does not serve as a guide 

 after a certain time, and even during vigorous life, if cut 

 down. Owing to unequal central development of growth, 

 there may be found three or four times more rings on one 

 side than another. Of course, when a tree reaches a great 

 age and begins to gradually decay, the ring-counting 

 process is no guide at all. For example, De CandoUe 

 records an instance of an oak felled in 1812, upon the 

 trunk of which he managed to count seven hundred and 

 ten distinct rings. That was proof to demonstration that 

 the tree had lived seven hundred and ten years, but as 

 De CandoUe pointed out, it had probably lived for three 

 hundred years longer than that problematical period 

 "covering the remaining rings which it was no longer 

 possible to count." Nor are the measurements of girths at 

 stated periods of exact scientific value under all circum- 

 stances — in fact, they are utterly unreliable if they date 

 back a hundred years or more. Perhaps the oldest oak 

 in this country still showing signs of life is at Cowthorpe, 

 in Yorkshire. It measures a fraction over seventy-eight 

 feet in circumference, and is probably from one thousand 

 five hundred to one thousand six hundred years of age. 

 The great oak at Saintes, in France, is dead completely, 

 its trunk having been scooped out and turned into a sort 

 of arboreal tea room ; but only a few years ago it had many 

 signs of life, and measured a little over ninety feet in 

 circumference. That oak probably lived close on two 

 thousand years. Dr. Schlich, in his Manual of Forestry 

 (Bradbury, Agnew & Co., Vol. I., pp. 1(j8), referring to the 

 disparity' of timber-life generally, says that "if grown 

 under conditions which are in harmony with their require- 

 ments," the yew lives more than one thousand years ; 

 the oak comes often near that age, "if it does not exceed 

 it" : lime, elm, and sweet chestnut, about five hundred 

 years ; beech and silver fir, under favourable conditions, 

 nearly the same ; ash, maple, sycamore, spruce, larch, 

 Scotch pine and hornbeam, three hundred years ; and 

 aspen, birch, alder and willow, rarely more than one 

 hundred years. 



Of course, in some respects trees never actually die ; at 

 least, that was Dr. Asa Gray's theory of arboreal life. 

 " The tree," he wrote, " unlike the animal, is gradually 

 developed by the successive addition of new parts. It 

 annually renews not only its buds and leaves, but its 

 wood and its roots — everything, indeed, that is concerned 

 in its life and growth. . . . The old and central part 

 of the trunk may, indeed, decay, but this is of little 

 moment, so long as new layers are regularly formed at the 

 circumference. The tree survives, and it is difficult to 

 show that it is liable to death from age in any proper 



