104 



KNOWLEDGE. 



[May, 1903. 



subservient to that of tlie great central colonnades under 

 tlie dome ; and yet it would have been dangerous to tamper 

 with tlie solidity of tlie shafts, since it is on the exedras 

 that devolves a considerable j)art of the thrust exerted by 

 the great arches, peudentives and semi-domes, and, in- 

 directly therefore, of the dome itself. A reduction in 

 height and diameter of the exedra columns secured their 

 subordination to the grand colonnades ; while the loss of 

 solidity thus inciUTed was in some measure atoned for by 

 the judicious choice of carmine Theban porphyry — the 

 strongest stone used in the chm-cli — as an eBective check 

 to the tremendous weight of the vaulting above.* 



If we revert to oiu- phm, in the March number of 

 Knowledge, we shall find that the abutments of the dome 

 are fairly satisfactory on all sides ; although ill calculated 

 to remain uubuttrcssed for many centuries in a soil visited 

 by frequent and violent earthquakes. But the abutments 

 of the lateral walls will be judged at once quite inadequate 

 to the wide spans of the aisles and galleries ; a defect 

 further aggi-avated in the angles by the additional thrust 

 of the exedras. It was, therefore, impossible for Justinian's 

 church to have stood long unbuttressed. Trouble must 

 have very soon made itself felt, first in the angles, then 

 in the midst of the north and south sides as well as to the 

 east, right and left of the Sanctuary, and lastly, after 

 several centuries, in the very abutments of the semi-domes 

 and of the dome.f Historical evidence confirms these 

 deductions to the letter. We find, accordingly, the south 

 porch, and of course the lateral ascents, in position as far 

 back as the reign of Theophilus, 275 years only after the 

 second dedication, whereas the sturdier piers of the nave 

 opposed, unbuttressed, a gallant resistance to the earth- 

 quakes of 754 years. 



But, in framing these criticisms, we should not be apt 

 to forget that, if the great architect, to whom we owe that 

 marvellous conception, showed himself fallible, in under- 

 estimating the effects of thrust, he was necessarily lacking 

 that experience which we acquire to-day by a mere glance 

 thrown on the buildinss of his time, now foui-teen centuries 

 old. Domed structures in the beginning of the sixth 

 century were comparatively new, few, and unimportant. 

 Nor could the vast, but grovelling, cupola of the Roman 

 Pantheon yield any object lesson in the propping of an 

 aerial dome at the height of 130 feet. 



A word or two on the solidity of St. Sophia in the 

 present day, and we will have finished with these disjointed 

 fragments. The part of the church which has suffered 

 most is the south angle, where the column of the gallery 

 has been thrust nearly 7° out of the vertical (Fig. 10). 

 But a strong double buttress, rendered immovable by the 

 weight of the minaret erected by Mohammed II., checks 

 any further inclination of the column. The arches to 

 north and south are smaller by 28 feet than those to east 

 and west, and, having j^roper support in the plan, are 

 fairly strong. As in the past, danger is to be looked for 

 in the great open arches to east and west. Inasmuch as 

 the four main piers are well buttressed from without, their 

 failing in a direction parallel to the lesser axis is an 

 impossibility. The age of the eastern arch is 540 years, 



* Probably these shafts were not long enough, so that they may 

 have facilitated, or even decided, the subordination in question. 

 In his work on Aya Sofia, Consfaniinople, London. 1852, p. 2, 

 Fossati Bays that during the reparations conducted by him from 1847 

 to 1849, he brought back to the vertical thirteen columns of the 

 Gyneceum which had been pushed out by the. thrust of the lateral 

 arches. G-reat credit is, therefore, due to Fossati for this architectural 

 triumph, by which he has so powerfully contributed to the con- 

 solidation of the church. 



t In his restoration of the exterior for 1300 (Fig. 3) the writer has 

 eliminated part of the buttressing of the aisles, with a view to 

 showing as clearly as possible the original design of the church. 



and this part of the vaulting seems to be in excellent 

 state, as the stone masses erected by Andronicus Paleologos 

 consolidate all the east front. But the western arch is 920 

 years old, and notwithstanding its buttressing, together 

 with the great niche, by an additional thickness, has been 

 deformed by the thrust of the cupola, the result being an 

 exaggerated concavity of the semi-dome. Moreover, this 

 arch has suffered much during the earthquake of 1894, 

 and its last repair has necessitated the removal of the fine 



Flu. 10. — Dangerously-inclined Column in the rigiit-hana 

 Catechumena, or first floor level. 



mosaic eikou of the Virgin at the crown. And thus it is 

 that tlie possibility of an eventual rupture of equilibrium 

 along the major axis, to the west, is the chief cloud in the 

 solidity of the edifice. Still, the danger is certainly far 

 from imminent, so that there are excellent reasons to hope 

 that the veneralile dome of the Eternal Wisdom, hallowed 

 hy the universal verdict of nations, and reverenced by the 

 ravages of time, will continue inciting, for long centuries 

 to come, the pious fondness and genuine admiration of 

 mankind. 



MODERN COSMOGONIES. 



By Agnes M. Cleeke. 



II.— CRITICISMS OF THE NEBULAE 

 HYPOTHESIS. 



Laplace's theory was a perfectly definite conception. In 

 this lay its distinctive merit ; in this also its special sus- 

 ceptibility to attack. Here was no question of condensa- 

 tions round nuclei arising at discretion amid the large 

 possibilities of boundless elemental confusion ; but of an 

 orderly succession of occurrences, rendered inevitable by 

 the steady operation of mechanical laws, and harmonising, 

 in their outcome, with the array of ascertained phenomena 

 visible in the planetary system. These, accordingly, ceased 



