The colours of the Book of Kells are remarkably well preserved after a lapse of one thousand years. Professor Hartley[450] a few years ago submitted the pigments to a careful examination and discovered the materials of which the colours are most probably compounded. He reported as follows: “The black is lampblack, or possibly fishbone black; the bright red is realgar (arsenic disulphide As2S2) the yellow, orpiment (arsenic tersulphide As2S3); the emerald green, malachite; the deep blue possibly lapis lazuli, but owing to its transparency when overlying green more likely not so. The reddish purple is either finely ground glass obtained from a solution of gold, or a preparation which was obtained by the action of a solution of tin and was very expensive. The other colours are neutral green like burnt sienna, a pale blue, and lilac.”[451]
ART METAL WORK:
We have referred to the fact that the pagan Irish were skilled workmen in metal. This class of work received a new impetus with the introduction of Christianity. The pre-Christian craftsmen exercised their skill in ornamenting shields, swords, sword-hilts, chariots, brooches, bridles, etc. as we learn from the specimens that are preserved in our museums.[452] In addition to articles of this class the Christian artists, the majority of whom were ecclesiastics,[453] made crosses, croziers, chalices, shrines to hold books or relics as well as book satchels in which both metal and leather were used.[454] Specimens of these may be seen in the National Museum, Dublin.[455] For real artistic skill the most admired specimens are the Ardagh Chalice, the Tara Brooch, and the Cross of Cong.[456] The designs and styles of ornament used by the metal workers were similar to those of the artists who illuminated the MSS. Artistic skill in metal work was brought to its highest degree of excellence in the tenth and eleventh centuries and continued to flourish until about the end of the twelfth century, but gradually declined after that date owing to the general disorganization of society consequent on the Norman invasion.[457]
STONE CARVING:
The skill of the Irish artists in stone carving is seen at its best in the great stone crosses of which about 55 remain in different parts of Ireland. One peculiarity of the Irish (or Celtic) Cross is the circular ring round the intersections, thus binding the arms together. This peculiar form was developed in Ireland and, once developed, remained fixed from the eighth to the twelfth century. Of the 55 great crosses 35 are richly ornamented and eight have inscriptions bearing names of persons who have been identified as living at various dates from 904 to 1150 A.D.[458]
The crosses have a style of ornamentation similar to that of the manuscripts and of the metal work. In addition to the ornamentation most of the crosses have groups of figures representing various events in Sacred History, such as, The Fall of Man, Noah in the Ark, The Sacrifice of Isaac, The Fight of David and Goliath, The Arrest of Our Lord, The Crucifixion, The Crucifixion of St. Peter (head downward), Eve Presenting the Apple to Adam, The Journey to Egypt. These sculptures are iconographic, i.e. they were intended to bring to the minds of the unlettered people the facts of Sacred History by vivid illustration. No doubt the preachers in their discourses directed the attention of their hearers to these representations; and perhaps they often lectured while standing at the foot of the cross with the people ranged in front, the preacher pointing to the sculptured groups as occasion demanded. It is probable that the figures were painted in brilliant colours like those used in illuminating the MSS. so that the people might see them more distinctly.[459]
MATHEMATICS AND SCIENCE:
We cannot close our discussion of the curriculum of Irish monastic schools without a brief reference to its limitations which are especially noteworthy in the case of mathematics and other secular sciences. While not venturing into details some writers manage to convey the impression that the scientific knowledge of the Irish monks was as profound as their knowledge of the classics. We have not found any evidence to support this view. The most that can be said in favour of the teachers of this early period is that they willingly imparted all the mathematical and scientific knowledge of their time. But the actual amount of such knowledge possessed by Western Europe prior to the tenth century was relatively small as compared with even the later Middle Ages not to speak of modern times.
ARITHMETIC:
Prior to the tenth century arithmetic was essentially the art of computation. It was largely devoted to computing Easter, so the terms “Computus” and “Arithmetic” became synonymous.[460] Apart from this practical side it is possible that a theoretical treatment of numbers was not absolutely wanting. The method of reckoning was necessarily crude and little progress was possible while the cumbersome Roman system of notation made computation with large numbers well nigh impossible. It remains for further investigation to show whether the arithmetical knowledge of the Irish monks extended beyond the limits of Bede’s De Tempora Ratione,[461] or equalled that of the Liber de Computo[462] of Rabanus Maurus. Our acquaintance with source material in this field is too limited to warrant any sweeping statement, but it is significant of the nature of arithmetical knowledge of this period and of the lack of creative ability to find a scholar of such ability as Marianus Scottus in the following century basing his work on Computus[463] on that of Rabanus. Indeed it was not until the introduction of the Arabic system of notation and Hindoo methods through Arabic influence that there was much possibility of progress in Arithmetic. The introduction of the Arabic system is attributed by some to Gerbert[464] (d. 1003 A.D.) but it was not until the end of the twelfth century that the Hindoo-Arabic system became generally established among mathematicians. A century later Arithmetic began to be applied to commerce.[465]