Byways in British Archaeology

With respect to the facts, there lies at hand a note-book containing the jottings of years, but so plethoric are its pages, that a mass of detail must be correlated and much matter shorn away before the case can be presented with any degree of lucidity.

“Things are as they are, and the consequences of them will be what they will be, wherefore, then, should we desire to be deceived?” Following the spirit of Butler’s philosophy, let us leave aside all hypotheses for the present, and review the facts. It will conduce to clearness if the particulars are summarized in due order.

The botanist will tell us that the yew (Taxus baccata) is a fine-grained, slow-growing tree belonging to the sub-division Taxineae of the Natural Order Coniferae, or Pinaceae. Its timber is tough, durable, and elastic, so that there is some truth in the New Forest proverb: “A post of yew will outlast a post of iron.” The trunk of the yew is deeply channelled, and its reddish-brown bark easily peels off. Looking at the narrow, leathery leaves, which are dark and glossy on the upper surface, but rather pale on the undersides, one might casually conclude that they are arranged in two rows on opposite sides of the twig. Closer inspection, however, proves that the leaves spring from all sides of the axis, but that a twist at the base of each leaf gives a false appearance of a plain double series[935]. The yew is dioecious, that is, the male and the female flowers grow on separate trees, but occasionally both kinds of inflorescence may be seen on the same tree. Over a large area of the Northern Hemisphere our familiar yew is met with, and an allied species grows in North-East America and Japan. The columnar variety (var. fastigiata), known as the Irish, or Florence Court yew, is said to have originated as a wild sport at Florence Court, in county Fermanagh, about 130 years ago[936]. Its outline looks very unlike that of the common yew, which has horizontal branches, and it has no further practical bearing on our subject.

It is important to note that the yew is demonstrably indigenous to Britain. It can be traced back not merely to the Neolithic Age[937], but even to the Glacial period[938]; hence there need be no debate concerning its possible introduction in later times.

Whether the yew be poisonous—no unimportant matter, as will shortly be seen—has been discussed frequently and at great length. The disputants often argue at cross-purposes, each side in turn misapprehending the exact point at issue. Having read all the literature which is reasonably accessible on this subject, I am convinced of the overwhelming proof that the yew has poisonous properties, though the noxiousness may be comparatively slight at certain seasons, in certain years, and with respect to certain animals. The results are most fatal when the beasts eat the leaves on a fasting stomach. When the leaves are dry and tough there is the additional evil of indigestibility. Yet there is an opposing fact. Mixed with three or four times their bulk of other food, green yew leaves are actually employed as fodder for cattle in times of scarcity. Records of this custom come from Hanover, Hesse, and other parts of the Continent. Stated in general terms, then, the poisonous principle (taxine) cannot be very intensely concentrated; it may even be inoperative until acted upon by the juices of the stomach. Again, the pulpy portion of the fruit is eaten with impunity, but the stones are considered highly injurious. Sufficient references are given in the footnote to obviate further discussion here[939], but it will be seen later that the modern theory was preceded by an empirical knowledge which harmonizes well with the ascertained facts.

The belief in the pernicious properties of the juice of the yew is, indeed, as old as Pliny, who tells us that arrows were dipped in the poison (toxicum), and that the hurtfulness might be neutralized by previously driving a brass nail into the tree[940]. He adds that some writers have asserted that toxicum was formerly taxicum, from the name of the yew (taxus). The assumption seems to be that taxus is connected not only with τάξος, a yew, but also with τόξον, a bow (τὰ τόξα = bow and arrows, and perhaps arrows only)[941], and φάρμακον, poison. But even if these links be allowed, the claim is vitiated by the refusal of the lexicographers to admit such a word as taxicum.

Caesar informs us that Cativolcus, one of the rulers of the Eburones, poisoned himself with yew[942]. Since a doubt has been raised whether the Latin taxus and the Greek τάξος accurately represent our word “yew,” it may be said that the latest authorities on both languages give that rendering to the respective words[943]. It must nevertheless be observed that there is an alternative word in Greek, for one of the several meanings of σμῖλαξ, or μιλαξ, is “yew.” Pliny’s word tristis (sad), applied to taxus, stands good therefore for the yew. It has been suggested that the Greek word is allied to τάξις, arrangement (from τάςςω = I arrange), the allusion being to the apparent double row of leaves.

Before leaving the philological section, some English equivalents of the word must be noticed. “Early Modern English” forms include yewe, yeugh, eugh, yowe, etc. These come to us from the Middle English ew or u, and these, again, represent the A.S. īw and eów[944]. A seventh century manuscript has a still earlier form, īuu, and this is said to be the oldest spelling in any Teutonic language[945]. There are, says the Century Dictionary, Danish, Old High German, Spanish, Old Irish, Welsh, Gaelic, and Cornish equivalents, and of these, the Celtic forms are possibly original and not derivative[946]. Professor W. W. Skeat supports the Celtic origin of the word yew, which, by the way, is quite distinct from the word ivy, although the various forms of yew and ivy suggest one another[947]. Dr Schrader says that the Old High German word iva, in the sense of “yew,” disappears as we go further East, and, in Sclavonic dialects, signifies a willow. The same holds good of the word for “beech,” and Dr Schrader believes that the change is due to the thinning out of these trees Eastwards. In Lithuania, again, the meanings of “fir” and “yew” run into each other[948]. Professor V. Hehn called attention to the same series of facts, from which he drew similar conclusions.

The older authorities followed implicitly the dictum of the Swiss botanist Augustin De Candolle, who, basing his conclusions upon a study of the annual rings of the yew, and upon the sizes of yews of known age, formulated the rule: An increase in diameter of one line annually. If we allow an average yearly growth of one line in diameter, we shall probably over-estimate the rate of growth for very aged trees (“il est probable qu’on est au-dessus de la vérité”), so that while we may, in practice, reckon each line of the diameter as a year, we shall, in reality, make the trees younger than they actually are[949]. De Candolle, in another place, admitted that for the first 150 years the annual growth somewhat exceeded a line in diameter, though for older trees it was less than this amount[950]. Abridging this rather involved statement, let us put the rule thus: Up to the age of 150 years the yews increase annually a line or a little more in diameter, and a little less than a line afterwards.

Since De Candolle’s day, it has been contended that his estimate makes the trees too old. Dr J. Lowe, in his interesting volume on Yew-Trees, has combated the conclusions at some length; his chapters are here freely drawn upon and compared with my own private notes. Dr Lowe’s estimate, taking young and old trees together, allows a growth of one foot in diameter for each period of 60-70 years. De Candolle’s rule would make a like growth represent 144 years at least (1 foot = 144 lines), or, supposing him to have taken the line as one-tenth of an inch—as some writers mistakenly believe[951]—120 years, or a little over. In the absence of testimony to the contrary, I think we may safely consider that De Candolle’s line was reckoned on the one-twelfth basis: indeed there appears to be no valid reason for doubting this. We note, in passing, that the calculations of Edward Jesse, the naturalist, made after measuring trees at intervals, agree closely with those of the Swiss savant[952].

Between the estimates of De Candolle and those of Dr Lowe, but far nearer to those of the latter observer, is the determination adopted by Sir R. Christison and his son, Dr D. Christison. Working on the eminently scientific method of measuring the increase of girth at a fixed point during stated periods, these observers decided that one foot for every 75 years would be more than the average rate of increase[953]. The three varying results may therefore be thus stated:

Mr J. E. Bowman, making use of the trephine, came to the conclusion that young trees may add two lines per year, and if the soil be very rich, three lines, but that, after a diameter of two feet has been reached, De Candolle’s limit of one line yearly holds true. De Candolle’s formula, Bowman considered, “makes old trees too young, and young trees too old.” Commenting on Bowman’s mode of experiment, Dr Lowe asserts that it has “no utility whatever,” because the external rings of the tree—those reached by the trephine—are not concentric, and are not formed in the same manner as those of the young shoot. Further, Bowman’s experiments seem to have been performed on young trees only[954].

The true estimate, therefore, seems to lie between the determinations of De Candolle and Dr Lowe respectively. The latter writer admits that De Candolle’s rule is fairly sound when applied to young trees with undecayed centres, but he stipulates that the tree must be cut down and proved to have not more than one centre. He refers to the case of a yew in Kyre Park, Worcestershire, which possesses two huge trunks, united below, and he proceeds to argue that, if we suppose the tops to have been broken off underneath the junction, and young shoots to have sprung up from the base, the trees would have been deemed as old as our most noted specimens in the British Isles. Such a case, however, would rarely be encountered in actual experience.

Fig. 69. Transverse section of yew, showing annual rings. Longest diameter, 5½´´; shortest, 4⅛´´; number of rings, 51. It will be noticed that the section is excentric; this is due to irregular growth. The light coloured, outer zone, is the alburnum, or sap-wood; the dark, inner zone, the duramen, or heart-wood. The large, radial cracks are the results of shrinkage. These cracks run along the lines of the medullary rays, though the actual rays are much too fine to be seen without a good lens. (For an excellent description of such a section, see G. S. Boulger, Wood, 2nd edition, 1908, p. 301.)

We will now examine De Candolle’s “ring method” a little more closely. First, what is the botanical theory respecting the formation of the rings in a tree? In our climate trees make little or no growth during the winter season, hence the new spring wood, with its wide, thin-walled vessels, is rather sharply defined against the narrower, compact, dense-walled vessels which were formed in the preceding autumn or late summer. The successive concentric cylinders of new wood, therefore, when seen in cross-section, appear as zones, or “annual rings.” These rings are well shown in the transverse section of yew (Fig. 69). In vertical section the rings appear as parallel strips, forming what is popularly called the “grain” of the wood (Fig. 70). It is true, in general, that one ring represents one year’s growth. The rule must, however, be applied under slight reserve. Dr D. H. Scott clamped the branch of an elm in June, thus increasing the pressure on the cells. The result was that wood was formed similar to that which is usually associated with autumn. After six weeks, during which the nutrition had been practically uniform, the clamp was removed, and another ring was produced.

Fig. 70. Longitudinal, tangential section of yew. In this section, taken with the “grain,” the annual rings appear as alternate parallel strips of dark and light wood. The tracheids, or elongated thick-walled cells, are invisible to the unaided eye.

The conditions just described were artificial and abnormal, but varying temperatures, if extreme, might act in a similar manner. Sequoias and red-woods may naturally form several concentric wood rings in a year, a result probably due to alternations of heat and cold. Against the danger of over-calculation of age from neglecting such factors, may be set the consideration that, owing to damage by frost, or to seasonal peculiarities, no ring may be formed within the year[955]. In normal circumstances, “one ring, one year” is a trustworthy maxim. Unfortunately, to verify this rule, should its accuracy be challenged, the tree must be cut down—a most undesirable proceeding. Moreover, if the tree be aged, counting the rings is a matter of some difficulty; one must use a lens and a pair of needles, moving these “counters” as if scoring at a game of cribbage. Now Dr Lowe, while doubting whether the yew may not form more than one ring per year—a contingency that would seriously upset all computations based on this system—feels confident that in this country young trees produce one only. He is of opinion that the ring test consequently holds good for uninjured trees up to 200 or 250 years. Beyond that period, he asserts confidently that the yew sustains injuries from storm or disease sufficient to invalidate the rule. To the extent, let us say, of 250 years, Dr Lowe’s assumption runs parallel with that of De Candolle, who believed that there is practically no limit to the age of the yew, except disease.

The errors to which De Candolle’s method is liable are thus epitomized. A yew which has been maltreated by lopping or injured by the browsing of animals may thicken and form bosses, and so increase the apparent girth. Trunks may be fused together. Wounds may prevent the formation of rings. Small shoots may be enveloped by the spread of the “bark,” and thus a vast number of rings may be formed which eventually become concentric[956].

Nevertheless, since we cannot always cut a tree down, some other method of estimating the age must be followed. And if the actual circumference be not always the true measure of the normal free-growing parent stem, our observations should, by way of counterpoise, be correspondingly numerous. Whoever has attempted to measure a yew, with the object of employing De Candolle’s rule, will recognize the force of Dr Lowe’s contentions, yet one cannot but think that the risk of error has been exaggerated.

We are told, again, that there may be a difference in the number of rings on the two sides of a tree, even at the same level, in other words, a given ring may not be everywhere of the same thickness. This is noticeable in the specimen, Fig. 69. In the famous yew of Darley Dale, Derbyshire, it is asserted that the number of rings varied from 33 to 66 in an inch of radius, taken horizontally—a curiously neat ratio[957]. Michel Montaigne, so far back as 1581, pointed out that the rings were narrower on the north side of the tree. Yet these occurrences do not hopelessly affect our conclusions. The writer possesses a section of a branch of yew from Offchurch, Warwickshire, which was over-developed on one side, the result of proximity to a stream, and of a sunny aspect. The consequent curvature of the heart wood, though certainly disappointing to the bowyer, who bought the tree, did not prove very troublesome even to the amateur ring-counter. Taking the average of a long series of years, and examining a large number of specimens, the inequalities in such specimens would be found to cancel each other. In an aged tree like that of Darley Dale, the coalescence of the rings would be far more perplexing than the unsymmetrical growth.

With respect to one source of error, Dr Lowe seems to answer his own objection. “A tree may have died on one side,” says he, “or may have ceased forming, while the other side is growing vigorously.” Yes, but in that case the error would be one of under-calculation; the yew would be credited with fewer years than the measurements warranted.

Once again, it is argued that not only may a particular ring have inequalities of width, but the different rings vary among themselves in thickness. And we have seen that growth does not increase uniformly with age. An oak of 50 years had a circumference equal to another which was four times that age. Nor is the rate of growth always uniformly diminished as the tree becomes older. De Candolle found an oak, 333 years old, which showed as great an increase between the rings of 320 and 330 as between those of 90 and 100 years. Now it is not mere captiousness to remark that these figures refer to an oak, not to a steady-growing yew, though Dr Lowe claims that the observation would apply equally well to the latter tree[958]. We may repeat: while variations in rainfall, temperature, and food-supply, correspondingly affect the rate of growth, it is a matter of common knowledge that our seasons tend to follow ill-defined cycles, and that a series of such cycles may be expected to equalize each other with a fair approximation to exactitude.

A far graver indictment of De Candolle’s figures is contained in the insinuation that his selected trees were stunted and ill-grown, so that the rate of growth was made to appear too slow[959]. The supposition, if well grounded, would severely shake De Candolle’s rule, but at present it is a supposition merely, as readers of the Physiologie Végétale may learn for themselves. De Candolle did indeed believe that trees die from accident or disease rather than from old age, but how could the bias resulting from such an opinion make the age of a yew greater than it actually was? An injured tree whose development had been arrested would be credited with too few years rather than with too many. Take the case of the Tandridge yew, in Surrey (Fig. 71). Aubrey found that this tree had a girth of 30 feet at a height of five feet from the ground. Manning and Bray, about 130 years later, gave the corresponding measurement as 32 feet 9 inches. To-day the reading is only 32 feet 4 inches. Allowing for some discrepancies in the modes of measurement, the results are striking. The explanation is that, though the tree is still vigorous, it has long been hollow, and growth must have been slight, if indeed there has not been an actual arrest for the past century.

The method, adopted by the two Christisons, of measuring a tree at known intervals of time, is perhaps open to less objection than that of assuming a mean rate of growth, based on the enumeration of the rings of selected specimens. A combination of both systems would be better, if not ideal. The “interval method,” nevertheless, overlooks the objection that growth is not quite uniform. De Candolle urged, as already noticed, that the rate diminishes in aged trees, and gave several reasons. The roots are farther from the air, and they are also working in competition with those of neighbouring trees. Should the soil be rocky or otherwise uncongenial the lessened elasticity of the bark retards growth. Add to these factors the likelihood of oncoming disease, and the slackened development would be appreciable. Against these considerations, Dr Lowe boldly affirms that “there is abundant evidence to show that old trees grow, at intervals, much more rapidly than young ones”; but he makes this concession: “they do not, as I have said, grow uniformly, but have periods of comparative arrest of growth[960].” These pauses, he believes, are due to the overshadowing head of the tree. Were the head to be broken every half century or so, rapid growth would again commence. But to what degree does such a pollarding occur in nature?

Does not the head continue, in the main, to overshadow the trunk and roots? (The lopping of yews for making bows, as apart from true pollarding, will be discussed later.) One reiterates, all systems are liable to error, but some systems are more accurate than others. And the “interval method,” especially if supplemented by estimating the total number of rings, according to an ascertained standard rate of increase, still awaits the coming of a better system to supersede it.